There seems to be a misunderstanding.
The point I was arguing is: filtering the results by exlusion tags is hard work for the server, and might be part of the reason why there is no multiple tag exclusion.
I supported this claim with the observation that one can make, while Itch is under attack by a ddos. Before Itch introduced this cloudflare protection, there were many, many ddos attacks, where you could observe this.
And the observation was, that the first things that fail, are longer tag combinations. Combining two tags might work, asking for four tags might not.
This was only speculation about plausible reasons why this filtering feature is missing and only exists as an undocumented and incomplete feature. I do not think it is the only or even the main reason. But such a thing will certainly influence a cost/benefit calculation.