They released GPT 6 Sol literally 6 days ago. We've accelerated to a weekly model release cadence. That seems like...a big deal.
It seems that 6.1 Sol is closely related to Astra. As for whatever 6.0 Sol was, it's anyone's guess. I'd speculate that 6.0 was just 5.6 with post training. It's possible however that it is the same model but with severe performance issues resolved so they bumped the version number.
They can release a new version every day if they wanted to. The question is whether or not the new releases provide substantial improvements or not. It's not hard to just go through the motions, bump the minor version, then make an announcement to rile up the users who don't get that none of this is standardized or regulated in any way and it's literally all made up by the company trying to sell them the product.