What I've noticed since a long time already:
It looks more and more like over average good CoO control gets showcased via in time CoA guards. It's really something. More "versatiled/balanced" haki users like Doffy, Luffy, Katakuri and even Don Chinjao have the greatest or pretty much the only CoA defense feats in the series.
Something that not even CoA specialized guys like Vergo or Zoro have- no hate, front or downplay. It's just that one would assume that it would rather go in hand with greater CoA mastery.
It really might be a legit quirk of "better" CoO usage. Take Doflamingo for example, who has no FS.
Dude hardly got hit w/o having a CoA guard on, even during the Rhino Schneider speedblitz.. Same was up with Luffy, even before he got FS.
During the Snakeman fight, Luffy and Katakuri could even put up haki guards while brawling it out at the same time at super high speeds.
I dunno if those guys would eat Marco's attacks the same way. Obviously I get that it's somewhat a Marco hype chap, but still. I'm eager to see if that changes within King's and Queen's major arc fights though. Those two would pretty much confirm whether all that is true or not, granted they are very powerful high tiers.
And again.. Marco's moves are so freakin smooth. Dude... Hopefully there's much more to come.