I really don't buy the suggestion that this is part of some master plan for a revised brand. At all.
1 - we have seen it used for 2 new products - both of which are international products from BBC Studios as far as I know. It has been seen nowhere else. Indeed the only other brand update which was done after BBC Select that I know of was BBC Studioworks - which seems to my eye to use a different version of the logo again (with Gill Sans but more padding inside the boxes).
2 - anyone with a gram of branding knowledge on a corporate scale knows that if you are going to change such an integral part of your brand, it needs to be noticeably different to what you already have otherwise you end up with lots of slightly different logos floating around and a diluted brand. Look at Morrisons - you had the black and yellow logo, then the slightly refreshed green and yellow logo, both of which lived side by side in half-hearted store refreshes. It was only once the current leaf-like branding came along we started seeing the brand properly updated across the portfolio.
3 - the BBC could not justify to the public/press expenditure on a huge rebrand politically right now, especially one with a logo so similar to it's current one. It just wouldn't fly.
I sure do hope this is true. It seems to me the most plausible explanation at this time and we will have to sit tight and hope further branding refreshes don't follow this same poor branding trajectory. As said, the correlation is that both of these logos are BBC Studios owned brands which in my mind are pretty far flung branches of the BBC. If more central brands in the UK begin to use this awfulness then I reckon we're in for trouble with the BBC's branding. Years and years of switching between Gill blocks and god-awful Reith blocks!
But as said, it wouldn't be the BBC's best interests right now to be rebranding it's corporate identity with something so subtly different. They introduced the Reith typeface in 2016 and I remember the typeface designers explicitly stating that a rebrand of the iconic logo was not in the plans. Obviously that's nearly 5 years ago now and things may have changed, but surely they would've introduced a logo redesign with the introduction of Reith in 2016 if they really wanted to do that? We've had many logo rebrands since then including News, Sport, Weather, Local Radio, Studios, Wales, Scotland etc. who have all used the masterbrand BBC blocks, just changing the division's typeface to a form of Reith.