Re: Committing or fence straddling???
Yes agree. Sounds like you've taken this seriously and done all the right things. Mites just won't suddenly wipe out your hive without warning, although the warning is easy to miss if you don't monitor. Doing things like mite counts, looking for signs of DWV, and checking the health of the brood can let you know in advance if there are any mite problems so you don't treat unless needed.
Being asked to feed antibiotics might be a concern. Although it shows the vendor was conscientious and ensuring your bees would be in good health, it also is a practise used to control a bee disease, AFB. Which could mean the package bees came from somewhere that is using antibiotics to control AFB, ie, there is AFB present.
My suggestion is google AFB and become familiar with how to recognise it. Then monitor those hives, if you can go treatment free and AFB free for 12 months it is almost certain there is no residual infection.
I may be jumping the gun, it could be the guy had no AFB, and also it is uncommon to get AFB from package bees even if they come from an infected hive. But it would still be a good idea to educate yourself on it and keep an eye out for 12 months just to be sure.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).