Is part 141 ground school really supposed to be 35hours?
A Ground School Syllabus needs to be checked and approved by the FAA.  As part of that approval, they will decide if it meets minimum requirements, and is expected to take the required hours.

If the actual delivery of the material in ground school takes a bit less (or more) time than approved, that is OK, so long as the approved syllabus is closely followed.

Source: https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_141-1B.pdf