Apparently delivery trucks are supposed to double park next to, rather than on top of, the bike lane. I don't think I've ever seen that. Also, since most (all?) bike lanes were added to existing streets, it would be my guess that the vast majority of one-way single-lane streets with bike lanes do not provide enough space for trucks to double park in the legal manner while still allowing traffic to pass by on the other side.
I also maintain that double parking in a bike lane is far less dangerous to cyclists than double parking on the other side of the street from a bike lane, forcing moving traffic into the bike lane to get by. Still not ideal, but the lesser of two evils if you want to permit double parking to any extent.