No, but in Colorado a chemical test is not needed in every case to prove a DUI. Like in many states, Colorado has two rules for DUI.
The first, which most people are familiar with, is that driving with a BAC of .08 or more is automatically a DUI. The state does not need anything more for a DUI in that case, but of course it must have the chemical test to prove the BAC.
The second is that one is guilty of a DUI if there is evidence that the person was driving a vehicle while impaired by alcohol or drugs, regardless of the amount. Thus, even one beer can be enough to get a driver convicted of DUI in Colorado if the state can show impairment. An since the amount doesn't matter, no chemical test is needed to prove that the person had taken alcohol or drugs before driving. The state just needs something that proves the driver had been drinking or taking drugs. This is one reason why I tell drivers to never answer the question the cop asks "Have you been drinking?" when they have in fact been drinking. A lot of drivers seem to think answering "one beer" is safe since that one beer wouldn't put them over .08. But that admission makes one element of the state's case: the driver had taken alcohol or drugs before driving.
Here, if the officer had evidence that the OP was under the influence of alcohol or drugs (and smelling alcohol on the driver's breath is typically good enough for that) and had evidence of impairment that's good enough for conviction. I agree with you that declining the FST was a good idea. The FST is not required in Colorado and very rarely does it ever benefit the driver to do it. But it certainly can help make the case for the state when the officer says the driver failed the FST. However, we lack some important information here. We don't know what the officer is saying is the evidence of impairment. The lack of accident details makes wonder if the accident itself is the basis for the impairment. If the accident was a single car accident or the circumstances of the accident clearly make the accident the OP's fault, then that accident can serve as the evidence of impairment.
If the accident is not the basis for the impairment, then the state's case will be harder to make because without the accident the officer can only go by what he observes of the OP at the side of the road. If the OP wasn't slurring his words, stumbling, having trouble focusing or paying attention, or otherwise showing signs of being affected by the alcohol then there wouldn't be evidence of impairment. In that circumstance a great deal depends on what the cop says he saw as evidence of impairment and what evidence the OP may have to counter the cop's claimed observations.
My guess is that the officer told his commanding officer that the OP does not appear impaired...and to cut their losses. If the OP was visibly drunk and there was an accident, you can bet the officer would have waited for the necessary evidence. I even find it strange that the officer had to wait in line. I'd say that the whole thing was rigged...and even punishment for refusing a FST and breathalyzer.
Do you think a good DUI lawyer would roll over on this or stand his ground?
The OP was charged. So the the cop had to have told the DA something that indicated the OP was impaired. I don't know what that was, so I can't say how strong or weak the state's case might be. It might be strong, it might not. That's something the OP's lawyer (and he should get one since he's been charged) will review and assess how good a chance the OP has to win if they take it trial.
I think a good DUI lawyer would review all the evidence in the case — i.e after getting the discovery from the state, talking to all the potential witnesses the OP has, etc — and determine what course of action would get the OP the best outcome on the charge.
We don't know the state's case. Without that it's really not possible to say how strong it is. And in a criminal case, it all starts with the strength of the state's case. The state is the one that has to prove the defendant guilty beyond a reasonable doubt. The job of the defense is to attack the state's case — poke as many holes in it as possible. Bear in mind that criminal law and procedure, as well as what juries are likely to do, vary from place to place. Colorado is different from your state of California. So what you are familiar with from California may not be what the OP will face in Colorado. Moreover, in Colorado, it'll make a difference where in the state this is taking place. There is a distinctly different outlook in, say, Denver than in Grand Junction. Which is why the OP is going to get his best recommendations and advice from a Colorado DUI attorney, preferably one in the part of the state where the case is being prosecuted.