Why is that? He's just become a Super Saiyan. He can train in the form. Shouldn't that make his progression better now?
All in all this is what we have...
1) Yardrat Goku > Trunks >= Gohan >> Cyborg Freeza >= Goku Namek > Freeza
2) Future Androids >> Trunks >= Gohan > Future Androids (Less than Half) > Gohan 2 Arms
Those are the factual chains.
The question then becomes, how does Future 17 (Less than Half) match up with Cyborg Freeza? The whole series seems to get more and more outrageous, it probably makes sense to have Future 17 > Cyborg Freeza and some would make the case than even 2 Arm Gohan to be above Freeza.
It's quite possible that Gohan does not know how strong the Androids are, decided to at least surpass Freeza before he gives it a shot against the Androids. There's a lot of ways you can make the story work here. I think most are comfortable with at least Future 17 Suppressed being at least on Freeza's level, if not higher.