Yes, you can be "subthreshold" but you could also be unconsciously masking.
When I was wondering about myself and thinking about seeking a diagnosis I thought about what I wanted out of it. It made sense for me to pursue one. Turns out I'm way more autistic than I thought lol
Self diagnosis is valid as fuck, and so is just recognizing traits that cause friction in your life and addressing how to exist with those traits in this hellscape. You don't need a diagnosis self or not to do that.