I would be far more sympathetic to these sspl corporations if they subjected themselves to those same license terms. But instead they play this some animals are more equal than others game.
That wouldn't ever make sense though. They're the licensor. You don't ever need a license in order to use intellectual property that you own. By definition the license is what allows third parties to use or redistribute copyrighted software.
No, legally what is being suggested above is nonsensical.
If you own the copyright to a work, you can freely use that work, and you can license it to others. As the copyright holder, you get to decide what terms go in that license, but you do not need to abide by those terms-of-use yourself since you are the licensor, not the licensee.
Suggesting otherwise would be a bizarro-world where musicians need to pay to listen to their own music, authors need to pay to read their own books, and so forth. That's completely absurd, nothing works this way.
There are certainly valid reasons to be upset at a software company for changing the license for new versions of its software, but this is not one of them!
They're total hypocrites! For instance Graylog switched to OpenSearch to reap the benefits, but themselves push the awful SSPL on their users.
I have no respect for these organizations. Provide real open source software or start up closed from the get-go, don't build on community contributions for a while and then switch to closed while marketing as being open!