My issues are high up in the gastrointestinal tract too - burping, spaciness, fermentation, bloating. I share the same detection concerns as you.
It is the cysts that were picked up in the 1st swab I did - both giardia and blastocystis. They turn into cyst form before exiting the bowel, so I tink the test may still be useful for those of us with symptoms high up.
I wish there were another way. I suppose a sample taken during an endoscopy might determine the bugs too.