UE4 doesn't support .st Files?

So, I’m using SpeedTree for ue4, which exports as an st. file and according to speed tree this should import to ue4. But, when I go to import ue4 Doesn’t acknowledge the file and instead asks for a .srt.

What am I missing here, Speed tree is very adamant this should work

Any help is appreciated

Thank You,
Andy

https://store.speedtree.com/ue4/

I have followed this tutorial before but, the issue is when I import, I can’t see the .st file which is essentially my only issue.