I believe James felt compelled to push his voice higher, as it was impressive to reach this register, but the number of shows on the I&W tour wore down his vocals, hence the scratchiness.
A simple listen to some of their live performances in 92 demonstrates what James was trying to achieve before the his voice became strained in 93. He hits it nicely in Killing Hand, live in Long Island in 92 (Home Sweet Home bootleg). He also hit it cleanly many times in his Winter Rose days.
No, he didn't have to try to push the register, but DT were all about showing off at the time, and this was James' "see what I can do" moment. His vocal approach at the time was to belt it out with fury, which only wore out his voice more on the I&W tour.