Yeah-it's definitely linked to testosterone exposure in the womb. The average ratio is 0.99 for a 'woman' and 0.96 for a 'man' (not sure if that would be gender identity or birth-assigned sex...). Ratios above 1 are a longer index finger, ratios below 1 are a longer ring finger.
Me...I'm an FTN. I discovered the finger-digit ratio when I was questioning, and I looked down at my fingers and was all like "EVERYTHING MAKES SENSE NOW!"
I once took a test that said it would figure out my brain sex (it came out as neutral-go figure-though I'm diagnosed autistic and autistics are considered to have extreme male brains, so I'm going with that). It had my finger-digit ratio as one of the questions on that test...I discovered my ratio was 0.85 on my left hand and 0.8 on my right

Now that makes me wonder how I ended up with a vagina