The stock ROM does not update your hboot. I'm not sure how you unknowingly upgraded, but I guarantee its not this stock ROM. That's not possible. That firmware is not contained in the ROM.
If you want to downgrade, you'll probably have to run an older stock RUU. Captain Throwback has older hboots in his firmware thread, but I believe you can only flash them if you're s-off.
As far as your flashing issues, it was because you're s-on. I had a difficult time getting that working right. I finally fixed it in my SharkieROM-LTE v2.5 s-on version that I posted at xda. All apologies for not updating this thread with that version. In any event, I'm glad you got it working.
Thanks for taking the time to stop in and let me know.
Sent from my EVO on the PPCGeeks App