@gwzcomps for what it's worth, my experience with IS has been that for individual new in box consumer goods that are common and would be easily identifiable by a specific Brand/MPN/UPC, it can be helpful to put all that info in because it is used in search/filters.
The worst consequence I have seen come from choosing to put "does not apply" instead is that you may not rank as high in search for the same products as other sellers that do put those specifics in and/or won't be shown if a buyer uses those specific filters to narrow down their results.
In a situation like I described where we use it when creating unique kits/bundles of products, that isn't really a factor because there aren't other people selling the exact same thing - which is actually the whole point of creating those bundles. 😊 I would assume your mixed lot listings are similar in that regard.
I would say if you can't verify any of the required info, use "does not apply" and see what happens. If they are more unique/harder to find specialty items, I'd be willing to bet you won't see much if any affect on your search placement from that - if they are items that are in demand, they'll probably still rank OK organically from your title.
This may all change and like you said in the future they may program bots or something to get tougher on this, but if the goal is to keep selling stuff now then I would say deal with that if/when it happens and for now, do what you gotta do to get your stuff listed and sold. 👍
