1) Unless you think sanji vs queen deserves 2 chapters, if not, Jack's fight should not warrant 1 whole chapter.
What we can argue is if Jack's fight deserves half a chapter or not.
Robin had two chapters against BM, Jinbe against WsW and even if we count Sasaki vs Franky had 2chapters.
In compare Jack should at least have one fight chapter and as I said, Oda offscreen the battle, he not show anything of Jack based on the hints.
2) You have to take into consideration that Jack has already gotten more screentime than queen + king. That dude's been on screen since end of dressrosa and zou.
Screentime doesn´t mean fight based screentime in general.
How many named attacks has Jack so far?
And since Zou his battle where shown in offscreen, we never see him actually in a battle.
As I said we speak about a important commander and he get less fightscene then Fuku vs Raizo.
That is actually sad.