Are they FWB or is he lying?

Hello everyone,

I find myself in a weird situation and I don’t know what to think anymore and would love your input.

2 months ago I started dating someone who told me he was in a FWB relationship with his roommate (been 2 years)

They have a rule: never inviting people they have sexual relationships with to their house. Although she did some times as it doesn’t bother him but HE never did because he thinks she wouldn’t like it. Either way the common spaces are off limits for the person invited.

I naively thought that this rule only applied to hookups but apparently it applies to everyone, even if they’re dating someone seriously.

The guy told me they have never thought about what would happen to the rule if one of the two started dating someone.

This got brought up again today as we were planning to meet (at my place as always) and he was complaining about having too much stuff to do so I suggested we go to his place tomorrow that way he could do his stuff and we could still hang out. (One of the stuff he needs to do is decorating the house for Christmas which I also enjoy doing) I even said we could avoid PDA and we can play board games all three of us. He said « lol I don’t think she would like that ».

Supposedly she knows about me and they’re not in love or plan to be or a couple. And he said he was very much emotionally available for love and a serious relationship.

Do I lack understanding for not being able to understand this whole thing? Is there anything I’m missing here? Why would she be so bothered?

Other than this, things are going great and I really do appreciate him a lot and I think it’s reciprocated.

Please help shed more light to this :)