HA! The wormhole.
The good news is that if you research long enough on the internet you can prove almost anything, or disprove!
I've got 8, 6V batteries wired in 2, 24V strings of 4 each for my house batteries. That system is 24V and solar charged. The bus is still 12V but also has its own small solar panel just for good measure. My systems are not interconnected, but I might down the road pickup a 24V to 12V converter for just in case moments.
A lot of those RV forums don't impress me. Not to offend, but there are some really smart people on here. We're a different breed.
I will say this, however, if you use your bus alternator to charge your house and chassis batteries at the same time, make sure that if one has a dead cell or is older than the other or whatever, that they charge evenly. Maybe this is what they were talking to on the rv forum. If you just wire up several different makes and kinds of battery to an alternator and try to fully charge them all, over and over, the liklihood that the weakest battery will pull down the others increases. This isn't really the alternators fault. If multiple, different kind battery banks are going to be charged, they need to be isolated from each other as a general rule for best results. This isn't to say that a lot of people dont listen to this advice and get on just fine.
Something like this is pretty clever
1315 Sure Power Battery Separator | Connector Concepts, Inc.