Whilst the figure is likely inflated, the sheer scale of the front and numbers involved makes figures like that not impossible.
There is a general level of attrition that occurs every day independent of assaults (as you elude to). Think the usual suspects, but in particular, from *yagas/drone dropped mines/FPVs etc that can penetrate further into Red territory thanks to LEOsatcom*.
If we leave out the river (which sees its own action), there is roughly 1000km of manned front. 30,000 losses per month is *1 loss per km, per day*.
To put that into perspective, let's go with a 10km chunk. With 30km penetration from 'the edge', that's roughly an area this size. I've used here so you can get an idea of the layers/positions/density involved. 10 losses per day.
'DRG' group gets wiped, guy steps on a cupcake, ATV runs over a mine, Yaga scores a couple of hits - there's your ten already. Now add in the probing groups, sector-wide assaults with armoured columns and more regular rotations... See what I mean?
Obvi, this will vary by sector, but that underlying attrition will scale accordingly by presence. 30,000 is possible. Certainly if it's casualties and not KIA.
As an aside the scaling for casualties the quoted post uses is nonsense in Ukraine. You're lucky if you are wounded and make it back. Someone mentioned 1:1 KIA/wounded recently IIRC, but I'd doubt that - at least, on the red side of the zone.