Your link does not estimate overall casualties, only deaths that can be expressly confirmed through Russian social media. It provides a good minimum, but it’s important to consider that a large number of those conscripted are from extremely rural communities and remote ethnic minorities within Russia who do not have access to social media, and so wouldn’t be represented in those statistics at all.

It's not just social media, it's official published data such as funerals, obituaries, and so on. It probably doesn't account for all the losses, but it's definitely a good representation.

Your same source mentions that their investigations suggested 47000-50000 deaths as of May 2023, and a great deal of the more intense fighting has happened since then.

Again, most of the fighting that happened since then favored Russia because it was the Ukraine on the offensive against heavily mined and heavily fortified positions.

Assuming Russia has a better death-to-casualty ratio than the average WWII army thanks to modern medicine, we’re looking and anywhere from 1:6 to 1:10, which would put casualties as of May at 300,000-500,000.

Not sure where these numbers are coming from since Ukraine doesn't publish their numbers anywhere. But, the casualties that are generally attributed to Ukraine are anywhere from 100,000-300,000. And Ukrainians are the ones losing 6-10x more troops because of their artillery disadvantage. This is explained in detail by Mearsheimer here with sources and references.

Every Russian adult male has served in the armed forces as part of the compulsory year of national service, so their conscription pool can be assumed to have some experience already, and seeing a near total replacement of fighting men about two years into the conflict is consistent with historical armies in trench warfare.

I'm sorry, but this is the kind of arm chair general tactics that NATO pushed Ukraine into and we see the results. Ukraine was part of USSR, and adults were also conscripted there. Pretty clearly that doesn't translated into an effective fighting force on the battlefield.

Britain and France in 1916 had exhausted essentially all of their pre-war trained soldiers by 20 months into the war and were relying on conscripts.

This is not what's happening today in Ukraine.