Not sure where we are without seeing some pictures, but I've only heard of buckhorn pruning -- if that's what he did -- citrus trees and avocado trees so far after pretty obsessive Internet searching of fruit tree pruning techniques over the last four years or so.
You CAN pretty much POLLARD apple trees but that I believe is usually done with old neglected trees that have lost production vigor due to significant neglect, and not so young as 5-7 yr old trees (?)
I have to note, though, that most pruning books caution not to remove more than 1/4 to 1/3 of each branch when making heading cuts and not more than 1/4 to 1/3 of entire branches when making thinning cuts, and not remove more than 1/3 of the entire tree at a time. Otherwise, you can send them into "shock".
-- yeah, mostly "book" knowledge with smattering of experience with my own few trees in the last several years -- folks with more hands-on experience may be able to advise better on the specifics... But here goes
The theory with deciduous trees is that when they are pruned while dormant, all the energy that had been sent down from the leaves and stored in the roots in the fall will now be concentrated in growing the remaining branches and growing buds. So you get vigorous re-growth in spring and during the growing season. Latent buds that would not have grown before will be forced into growth.
Assuming correct precautions were taken not to introduce any diseases due to cutting larger limbs and these trees remain healthy, if they have been pollarded, what you can expect is A LOT of shoots explosively growing all over the trees this spring. And these need to be carefully thinned to create a new desirable scaffold/branch architecture for the trees.
I believe some apples bear fruit on the branch tips, but even then, the fruiting buds I think develop from existing buds from last year's growth. Typically though, I believe the goal is to develop fruiting spurs along established scaffold branches. What kind of apple varieties do you have?
As for care, you may need to be extra cautious of diseases and burrowing pests entering the cut surfaces, and be on the look out for pests that will target the tender new buds and shoots. You may not be able to use as strong measures on them... I'm not sure.
Mostly, I would spread compost if you didn't in the fall and mulch well. Don't feed excessively (if at all...) -- compost should be enough since all that energy is going to come back up from the roots, and overfertilizing can lead to weak pest-ridden growths -- and be prepared to prune carefully this season. Maybe your boyfriend knows what he plans to do?
In my humid summer climate, I have a period during early - late summer when fireblight is a significant threat and I shouldn't prune. Do you have to watch out for that too?