It might make seem to be reasonable to have these protected lanes for slower? cyclists in addition to allowing vehicular cycling, but there are two problems with this: a) it encourages car drivers to assume bicycles should not be in the lanes; b) it discourages cyclists from joining the flow when they're ready
As a cyclist, I'll gladly use separated infrastructure if it's fit for the purpose -- limited use trails that go where I want to go are great; separated bike lanes on big climbs are great.
Separated lanes that don't allow me to turn where I need to are unusable. Separated lanes that throw me into the flow of traffic from the right of parked cars with maybe 10-20 feet until the intersection where drivers are going to stop on green to turn right onto a crowded street are a death trap.