People on the forum either don't know that NTR has subgenres or choose to ignore the fact and I'm fairly certain F95 doesn't have either "Netorase" or "Sharing" tags, where such a scene (like the guards gangbang) would fall into. There's "Swinging" but that's not exactly just giving your partner over but rather also taking action on anothers' partner.
It's just about whether it fits the forum rules for
NTR or not. People arguing about the definition often kind of miss that point. Refusing to tag a game properly isn't really the way to go about disagreeing with the site wide definition. Only issue I'd say is it's a bit vague and that makes a solid agreement difficult.
"
NTR [Designed to cause jealousy by having the romantic interest involved with someone other than the MC.]"
Some people will consider any character involved with somebody other than the MC in a harem game for example to be NTR here. You could easily say that a harem game is designed to focus all the characters at the player and the player alone. Leaving the definition up to the player's feeling can cause problems like that. It should probably be something like "A romanatic interest can be fucked by a third party against the player's will and/or is unavoidable.". That would make it more consistent anyways.
Swinging does fit the definition better when considering what tag to use for the MC allowing their partner to bang others btw:
"Swinging [A couple allowing one or both partners to have sex with a third party.]"
I think there's no netori tag because it's super common to bang somebody else's love interest, though yeah, that tag should probably exist. Netorase seems close enough to normal netorare/swinging to not really need a distinction I guess.