At that temperature you are not "burning off" all of what you are thinking.
Decarboxylation of THCA has a time and temperature range need the covert to THC not to mention the other cannabinoids, 220f is on the low end of decarboxylation, beside what you are vaping at that temperature there is a whole world of other cannabinoids that have not reached their boiling point or have just be converted to another form.
Delta 9 THC boiling point is 311f
Delta 8 THC Boiling point is 347f
so if you are not reaching those temperature you are not expelling all of Your Thc not to mention the other cannabinoids and terpenes that remain for your alcohol extraction to grab.
I just throw away my ABV bud and use top shelf nugs for tincture.
Do you know for a fact that your vape pen works at 220f?