I know you like being pedantic so here's some pedantic facts
The Pentax 67 is a tiny bit heavier but is more comfortable to hold and use and if you factor in the 6x7 factor then there is no weight penalty. The Mamiya 6 is 6x6, lighter and better handling but is not an SLR. Then again, there is always the Bronica SQB which in a like-for-like config like a Hasselblad weighs a tiny bit less.
Like for like if you are talking about a Rollei 6000 series then it should be compared to a Hasselblad EL, so for example a 6008i (like the one I have) compared to a 500ELX (like the one I
had) is a bit lighter.
So, if we are being pedantic, which I'm sure we all appreciate here, the Hasselblad is not the lightest whichever way you look at it.