Guild offered in the wrong place

[DVX BELLORVM]

Aren't those contradictory?

Indeed they are
The second statement was written after better reading of the above mentioned guide... in the meantime I forgot about the first one
I've edited my original post and corrected the mistake. Thanks.

With some guilds wouldn't the loss of 20 points be prohibitive?

IMO, no. Anyway, I was mainly referring to thieve's guild, I have many of them (or rather had many of them ), and I won't miss them if I never get another opportunity to build another one. Besides, each spy trained gives you 10 points, so loosing 20 points is not a problem. This is the case with most guild types, as training of a unit that gains points usualy adds 10-15 points.

I think the only guild type that could suffer that loss are the Crusader Knight's Chapter Houses.