I'm in a colder zone than you, so take that into account, but I do have 2 apple trees and 1 pear tree (plus plums, sour cherries and other fruit). I generally do not fertilize my fruit trees at all, for the reasons you mention. I have in the past and my sense was it created more of an issue with loose growth that attracted aphids rather than delays in hardening, but that was for spring fertilizing so maybe it was early enough to not affect fall ripening of the wood.

I would definitely not fertilize my fruit trees now. If you are really keen on giving them fertilizer, I'd recommend waiting until next spring. My 2 cents.

Hmmmmmm, I think youre pretty close to the end of the fertilizing season. IF too late, the trees wont harden off in the fall, and get damaged in the winter.

Im in what the books say is zone 3, more like zone 4 with 5 microcliates. Anyways, the moment the ground can be worked I topdress a 3 inch layer of manure around the roots about a foot past the dripline. Then I mulch the hell out of it to keep the roots cool. Once the tree flowers, i am now giving them a foliar spray of seaweed fert, with a decent dose in a circle around the dripline.

The last few years ive used blood/bone, which works but I seen better results using well composted cow manure.

I would wait for some other people to put their opinions in here, but I do know that the colder the zone, the shorter the season (generally), which means the shorter time to fert and have the trees harden off.

In a couple months apply some gypsum/ a little ashes widely dispersed around rootzone and a month later some urea.