I tested, and other bike routing software is also happy to make a turn here. I haven't used the layer=* tag very often myself, but maybe this line is coming into play? Also, looking at the Edgewood Avenue and Harrison Street bridges as a comparison.

"When ways are passing on different levels apply layer=* only to the way which also has the bridge/tunnel attribute. Only ways with one of the tags/attributes tunnel=*, bridge=*, highway=steps, highway=elevator, covered=* should be tagged with the layer tag, similar for railways and waterways."

I'd still think that 1 vs -1 shouldn't allow routing though...