Not sure about this if your information is correct then there is a huge error and splinterlands devs need to be made aware as everyone in all of splinterlands is making decisions based off of the rich list cc @cryptomancer
From what i understand all of these accounts listed are representative from the SPLINTERLANDS perspective aka what is in the IN GAME WALLET.
So accounts like @sl-hive is the totality of what is in the Hive-Engine system. I think that's why you think there are ~2.8b tokens.
There are a couple of -eth accounts which represent what is floating around in the ETH ecosystem. We know there is at least 334m DEC over in ETH so these numbers are close though with these two I only see 290m dec represented.
The diesel pools have about 900m DEC in them so of the 2.6b in hive-engine quite a bit is in pools... but lots of us have tokens just sitting in hive-engine instead of in game because of the feeling of more direct control over the tokens.
Anyway there are several other splinterlands teams account and 3rd parties who keep the funds in a sort of escrow specially when it comes to other chains.
I just hope people don't read your blog thinking there is only 2.8dec... the evidence we have is that there is significantly more. OR there is a HUGE issue with the data provided by splinterlands in this richlist. However I do tend to trust a detailed itemized list.