I mean 3 years can be a lifetime for fighters, and KSW judging can be dodgy. Since then he's dominated all of his opponents, and finished them all as well. Imo comparing the two Shamil seems like the more skilled fighter, finishing rate is identical but Shamil gave their first finish losses to Storley, Murad and Kunchenko which speaks to how deadly he is. Comparing that to stopping Taylor (4 losses by TKO), Silawi (5 losses by TKO), Ward (finished in all of his losses) and Bowen (.500 record and only 1 loss by decision) and I can see why the line became what it currently is. You're basically left with Umalatov having to lean on his wrestling across five rounds vs a guy who has shut down every wrestler he's faced so far, high level wrestlers, and who doesn't get overzealous chasing a finish and gassing. If anything Umalatov is the one who is far more willing to slow things down if he doesn't get a finish early.
I'm probably not backing him unless money comes in on Umalatov, but I do think Shamil has the edge based on what each have shown in PFL so far. He's looked flawless.