Wow! I agree with your line of questioning. I would like to know too.
I have three floor drains that I just installed. Venting is far more than 5' away on one of them. So, in the "worst" case you will have two drains with two P-traps and drain pines and the venting is far away from the P trap in one case. Not significant.
At least you have a trap primer. Believe it or not, a Master Plumber told me on Day 1 that he wouldn't bother with trap primers. Go figure.