Your decision, obviously.
If the lameness exam showed only the fusing hocks and nothing else, and horse seems to be HAPPY and riding well with their current management, I myself would not be turned away in the slightest.
Two of my four horses have fusing hocks. One is 19 this year and I have had him since he was 6 years old. He’s been fusing this whole time. Only one area on his right hock has fused completely (upper) where the vet can no longer inject. (So in my mind there is no such thing as waiting for the hock to fuse, because you might be waiting the horse’s entire life span.)
I inject them when they need it, give Equioxx if they need it (they also both happen to have navicular…) and their hocks seem to do just fine.
My horses usually have the winter off so I can usually get by with only injecting once a year. If we rode all year long, then they would probably need every 6 months.
I know there are plenty of folks who have had horror stories with fusing hocks, so that’s why this is YOUR decision, but mine have had easy management and haven’t hindered them at all.