We did that decades ago...and it was nothing like shatter. By modern extraction standards...it was low mids.
Well there's different methods, I did a qwiso and it came out amazing .
And the stems weren't from some low grade brown as shit dirt weed lol, I had top shelf shit, and it wasn't only completely stems I also used any shake I had but it was still high grade either way. High THC percentage.
Some people who even used the same method didn't get the same results that I got, and I don't know why but every time I do it it makes about a gram and a half of some shatter like hash oil.