Research income is reported as part of the REF, so it does make a difference there.
I am surprised, though, that you are allowed to use research funding for teaching buy-out like that. Except in very exceptional circumstances, we are only allowed to use research income to buy out teaching time if the funding covers us for more than the 40% of our time already allocated to research. And we are being discouraged from using teaching buy-out at all at the moment, even if we have grants covering more than 40% of our time.
There is still a net financial gain to the department if someone is appointed to do the bought-out teaching, simply because they are likely to be paid less than the person who is doing the research. Although obviously this gain is not as high as if you just tell departments with people who need buy out that they can't and they should just 'find a way to make it work'...
I think that universities are panicking a bit about how to balance their books and do the extra teaching necessary if we return to a face-to-face but still socially distanced way of teaching.
We have been told by the university that we can continue to do any funded research, but if our research is not funded (or not a continuing piece of work that would be ruined by stopping) then we are expected to put it aside and take on extra teaching. I guess reclassifying people without grants as research inactive is a way of formalising that move (or alternatively encouraging them to bring in some external money).
Likewise, if you have funding for conference attendance, equipment and so on through a grant then you can use that funding, but otherwise departments must cut all funding for these activities to save money. We are not even allowed to use the departmental kettle anymore, even though it is our kettle that we bought, because it uses the university's electricity!