soil is never a good idea for GTPs or any other python in my opinion. in fact, i believe it's on the list of substrates to be avoided, after pine and cedar. it may be 'safer' in the sense that it's non-toxic, but soil doesn't really hold moisture and will allow mold or bacteria to grow easily. it's also possible to get particulate stuck in the mouth or gums of your GTP and therefore poses a risk of infection. I'm certainly no authority and may be corrected, but I would not use it.

I use paper towels for my neonate and cypress for my adult GTP. cypress is cheap and almost as available as any kind of soil. and newspaper is the old standby for any snake if you're on a budget or out of options.