The way I've ended up interpreting bonus feats that don't declare either way is if something gives you a specific feat, you get it and can ignore prereqs, but if it gives you a choice, you have to meet any prereqs it has to pick it. I based it on the tendencies I've seen for the stuff that does have declarations, where it seems most of the time (possibly all) whenever a specific feat is granted as a bonus, you get it regardless of prerequisites, while usually when there's a choice, you have to meet the prereqs to take any given one. Of course, if someone shows numbers that would skew it in a different direction ...