a question about giveaway entry rules

You can also just use your SG whitelist, which will grant users immediate access to the giveaway(s), without them having to accept a group invite and resync SG. I personally prefer groups, as they're (imo) easier to manage. Also worth noting that you can't get a reroll if you remove someone from your whitelist but they've already entered your giveaway- but if the user is no longer part of a group when a giveaway ends, then you can still get a reroll.
So it makes groups a much more reliable option for things where the conditions in question may change (such as a user's SG ratio) over time. For your condition, whitelist may be a more useful option. :)

That said, you can always poke Knsys here to ask questions about, or make requests for SGTools. :)

Just keep in mind that everyone uses their wishlists differently. You may want to do more than a cursory check [as, for example, some small number of users wishlist every game they come across, win hundreds of games, have thousands of games in library, and only appear to have ever played the exact same 5 games]. One of the benefits of manual checking is, after all, that you can cater the inclusions to even better fit your criteria. :)