Hey Max,
What it comes down to, it is your "new" tractor, so it is your choice!
Now here is the thing, is it "Brand New" from the dealer or a used "new" to you tractor?
If it is used and just "New" to you then you have NO clue what has already been used in it, if it is "New" from the dealer then check with them to make sure.
Now having said all that, when it comes to my own cars, trucks, tractors and other equipment, I use whatever I can find or have on hand when I need it, I have "NEVER" followed the Manufactures recommendation when it comes to fluids and filters, I buy the brands I trust, and in the 40 years I have been buying my own cars and such I have never had one blow up or shoot craps on me because I used something other than what is recommended.
I buy 5 gallon buckets of Tractor Hydraulic/Transmission fluid from my local farm supply store for use in all my equipment, it has always served me well.
Best Regards
Paul