is there a difference between this construct and יותר גדול
No - יותר גדול and גדול יותר are exactly the same.
Then why do they reject יותר גדול?
Duo marks "זה יותר גדול בפנים" as incorrect. It only accepts the word order "גדול יותר"
Why? I thought adjectives followed in Hebrew. Please explain.
zeh gadól yotér beefnim
Why can't we use בתוך for "inside?
ll בתוך is a preposition, and required inside what.
I am inside the house = אני בתוך הבית
I am inside = אני בפנים
I love the Dr. Who reference, but I don't think we've learned comparatives yet, and until we do, sentences like this one shouldn't be used in lessons (this one was in Prepositions-2).
While you have a point, I think rare unexpected stuff is OK, it gives one some insight on what one is going to learn, lets one figure some things on their own.
How is בפנים pronounciated?
יותר גדול still not accepted