The difference here is the SM heads you get bare or assembled are garbage out if the box and the ported ones here being discussed are super well thought out from years of experience trail and error.
I have spoke with many porters and machine shops about the OOTB SM head and 90+% don’t like it and trash it while laughing at the fools that spends more money to fix the junk. Porting work additional.
If you know what your doing with the head to begin with and work the head yourself, you can not only be ahead money wise but end up with an excellent performing head, IF you have the machines and know what your doing to the head when porting time comes.
What we have here is a fella taking a bare head and making it great. Not the OOTB complete head.
How some guys can take that OOTB SM head and think they are going to use it as is and run in the low 10’s is beyond me!