I can't speak to Maryland, but at least for California, I don't agree.
Quoting That Guy
(a) A driver facing a circular green signal shall proceed straight through or turn right or left or make a U-turn unless a sign prohibits a U-turn. Any driver, including one turning, shall yield the right-of-way to other traffic and to pedestrians lawfully within the intersection or an adjacent crosswalk.
(b) A driver facing a green arrow signal, shown alone or in combination with another indication, shall enter the intersection only to make the movement indicated by that green arrow or any other movement that is permitted by other indications shown at the same time. A driver facing a left green arrow may also make a U-turn unless prohibited by a sign. A driver shall yield the right-of-way to other traffic and to pedestrians lawfully within the intersection or an adjacent crosswalk.
The pictures of the signs that you've posted are for Mandatory Movement Lane Control signs, and this is governed by VC22101:
(b) When turning movements are required at an intersection notice of such requirement shall be given by erection of a sign, unless an additional clearly marked traffic lane is provided for the approach to the turning movement, in which event notice as applicable to such additional traffic lane shall be given by any official traffic control device.
This doesn't say anything about U-Turns, only that if a turning movement is required at an intersection there needs to be a lane, a sign, or both. 22100.5 does discuss U-Turns:
No driver shall make a U-turn at an intersection controlled by official traffic signals except as provided in Section 21451, and then only from the far lefthand lane that is lawfully available to traffic moving in the direction of travel from which the turn is commenced. No driver shall make a U-turn at an intersection controlled by official traffic control devices except from the far lefthand lane that is lawfully available to traffic moving in the direction of travel from which the turn is commenced.
U-Turns at intersections must comply with 21451, and be made only from the leftmost lane. At intersections controlled by traffic control devices instead of signals, the movement must also be made in the leftmost lane of traffic flowing in the same direction.
All of this means that unless a sign is posted at an intersection that prohibits U-Turns, it should be legal to make such a turn. The CA-MUTCD supports this interpretation of the law:
CA-MUTCD 2012 2B.18:
Motorists can make a semicircular or U-turn on a green signal or green arrow except where such turn is prohibited by signs. Refer to CVC 21451 and 21454.
Local authorities, by ordinance, may prohibit the making of any turning movement by any vehicle at any intersection or between any designated intersections. Refer to CVC 22113.
The No U-Turn (R3-4) sign shall be used where U turns are prohibited except when Intersection Lane Control signs (R73(CA) Series) signs are used at signalized intersections with separate left turn phases. The No U-Turn/No Left Turn (R3-18) sign shall be used where both, left turns and U turns are prohibited.
The two sections after 2B.18 deal with mandatory movements either at intersections or in lanes. The 2B.19 section only mentions U-turns in the context of suggesting that the R73 sign be used instead of the R3-4 sign when U-turns are prohibited at a signalized intersection. The 2B.20 section, about mandatory movement lanes, states that the authority for this regulation comes from 22101, and that signs should be used "to indicate the type of movement permitted at a major intersection where ground mounted signing is not adequate." This means that unless there's a sign that prohibits U-turns, drivers should be able to make a U-turn from a Left Turn Only lane provided that it was otherwise legal to make a U-turn there. (E.g. it's the leftmost lane, done in accordance with 21451, and no local ordinance prohibits it).