He's an athletic beast and an incredibly well-rounded fighter, but we really haven't seen him fight truly elite competition at FW yet. In no way is he realistically ready for a title shot - here's the list of opponents he's fought and a quick synopsis of each.
Youssef Zalal - underrated scrapper and tough to finish, took him to a decision which is respectable in your debut.
Damon Jackson - another scrapper but primarily a grappler with poor striking defense, has been sparked early repeatedly before. Illia does what he does best and ruins his whole shit.
Ryan Hall - pure grappler with funky kicks as a distraction to get grappling engagements somehow. Illia just stays away and he results to trying endless Imanari rolls that eventually get him in hammerfisted into side-control and finished.
Jai Herbert - huge LW striker, but tall-man's striking defense and questionable chin. Almost kills Illia with a headkick, but he shows heart and survives to come back and just murder Jai when he is tired and on the retreat against the cage.
Bryce Mitchell - relatively unathletic but crafty grappler that has some underrated striking offense but poor defense. Comes in "sick" (or so he claims) and gets beat up for most of the fight, but he does hurt Illia with a body shot and have him on the retreat for an extended period at one point. But can't handle the power or pressure, wilts under the shots and basically gives up an arm triangle to escape the beating.
Josh Emmett - compact, powerful, predictable striker that wants to catch you coming in to brawl with him or trying to escape the brawl on the way out. Ilia just stays patient and throws crisper, straighter punches with tighter footwork and less predictability and just pieces him up.
My conclusion = he's feasted primarily on "specialists" in his UFC run - the most truly well-rounded fighter was Zalal in his debut. Jackson/Hall/Mitchell are all grapplers; even though Jackson has some decent hands and Mitchell has decent kicks they all have shit defense and ability to chain or build. Herbert and Emmett are pure strikers (yes I know Emett can wrestle but he doesn't really), but at least they have different body types and styles so it show-cased some different adaptability.
He honestly should be fighting Allen or Evloev - out of all the guys in the top 10 (excepting Volk) those are the most truly well-rounded fighters that would be able to test him in a lot of different areas and see if he is actually ready for Volk.
Problem is they are short on contenders so they could just burn one if they put him in those fights and he loses. They did that with Allen's 10-fight win streak against Max, they might not want to risk it again here with Illia.