Think I don't do my homework? One of the most referred to documents in the country for signs and signals is the source.http://mutcd.fhwa.dot.gov/pdfs/2009r1r2 ... dition.pdf
This version is more relevant than 2012 since the signal is older than the most recent edition so it wasn't installed under it.
Go to document page 829.
9A.04 says the signal shall command respect. They don't say that a signal has to be on a bike lane, facing the bike or what it has to look like. It says it's for a bike facility. That includes in street biking and if you look at doc page 845 this section covers shared use paths too.
So a signal meant to help motorists respect bikes, placed at a bike facility and following rules that don't require a bike-shaped signal.
Trolley Track Trail has a bike signal. A signal placed to improve bike safety, not at a bike lane signal. There's no other way to view it.
You're describing a type of signal head. I'm saying it's not the first bike *signal* and the head on the signal is irrelevant for the determination. A straight arrow in a middle lane says I can go straight. A circle says the same even though it can mean I can go right when mot in the middle lane. The signal head could have been a circle with a sign. The bike is clearer but not the only way