This is my whole point - they try to keep saves compatible, and put effort to fix any issues with save game compatibility.
My earlier response was to people saying that we should only ever test the Beta with new saves because it is "common sense".
Which imho would be hurting the testing process, skipping the whole part of testing save compatibility. And since the save compatibility is actively maintained already, with bugs that break it fixed with high priority, it is better to spot any new bugs that break saves here in the Beta, rather that later when Beta goes into stable. I am not saying that any compatibility breaking bugs must be fixed and 100% save compatibility maintained. I am saying that any compatibility breaking bugs should be spotted here in Beta, so devs know about them now, so they can either fix them, or announce that "sorry with this new version old saves will have problem X", if they deem it infeasible to fix.