Anyway, saving RealBand files in the *.SGU format, which is the default format, is WORTHLESS.
Wrong. Sorry.
First, all of us including me have screwed up in saving stuff. Hell, I've even wiped out the wrong vocal track because my eyes were going crosseyed and I wasn't paying attention either. Luckily I had the vocal saved as it's own wav file so I was able to import it back in but that was a bonehead move on my part because I still lost a bunch of current edits I had just done.
Consider this: You've spent 5 hours with Biab testing out different styles, different RT's whatever then decide to move it to RB. You save it to the default .SEQ. What did you just do? YOU JUST WIPED OUT THE BIAB FILE. IT'S GONE.
And as already mentioned RB will open a SGU file but Biab will NOT open an SEQ file so it's gone, baby.
There are many reasons I won't go into here why you would want to keep that Biab file as well as the new SEQ.
All I can say in a friendly way is pay attention, read the manual and stop with the ranting about "incredible poor design" and all that. DAW's are complicated and the manuals are hundreds of pages because everybody wants every possible choice there is for everything.
This is simply one of many choices you need to pay attention to. There's a multipage thread from last summer debating both sides of this exact issue. Some want the default one way, some the other so now you can set it yourself. This was just implemented last month.
Bob