So, I understand why #surprise_giveaways adhere to functionally the same rules as #trading_rules, because it's just doing a very one-sided trade, but basically still an "unmoderated" trade where neither Pokémon is verified beyond doubt. However the ones in #giveaways are thoroughly moderated, even saying "We are currently accepting giveaways of legendary/mythical Pokémon via #giveaway_queue" whereas they're banned from #surprise_giveaways.
Would it make more sense for the Proper Staff Approved Giveaways™️ to not be subject to tradebans? A requirement could be having them hackchecked in advance AND provide ample real world proof (video/photos of catching or redeeming it/the event code card/wondercard present in save/receipts or event ticket stubs etc.) for extreme rarity/"often hacked" mons.
As an example, a Shiny GO-origin Mew (otherwise tradebanned) wouldn't be difficult to verify if one of the requirements was "take a video of you transferring it into HOME from GO, showing the name, stats, etc.", on top of a manual hackcheck. Cheaters tend not to bother faking proof, (in cases like the GO Shiny Mew, it essentially can't be faked), they just hope you don't ask for proof.
If it can't be verified beyond doubt, then it doesn't make the cut.
Even then, you could still enforce the tradebans for those Pokémon in the rest of the server, so the giveaway winners don't attempt to re-trade them.