Check this. I wanted to stop but a word grabbed my attention:
spoilers
They are talking about it like it was movie: pls don't hurry to give out the good part.
They don't say: don't alert the enemy about our activity.
The enemy knows, the public don't.

There might be other reasons but here's two possible explanation:
1. They captured shit. They started half a year ago and they still where they started except they finally revealed that. So now they are in a situation where claiming captures is really premature. Their "infiltration" units managed to walk far, but got clapped by the bombing missions Clement noted happening. Right now, beside them noone really knows where they are, so OSINT researchers guessing about their advances. However these advances are way further than how reality is. But now expectations are high, and will suck balls when it turns out they didn't managed that much.
2. They did capture considerable area, towns villages, they are advancing more, the RuAF knows, but the AFU want to keep it quiet to release the info in a right time to have more impact on Russian election in November (they elect reps into the State Duma), and they want to cause as much turmoil then as possible.
How much any if this is possible I dunno.
I'm fairly sure however they don't give a fuck what I think for example.