When I did FETs at SG, they made me wait 2 full weeks between transfer and first beta, so equivalent of 19dpo. Seemed so excessive to me at the time. I did 3 FETs there, with the same requirement each time.
For my one successful pregnancy, I tested positive on a home test at 6dp5dt. I also had an ectopic from an FET and didn’t get a positive at home on that one until 12dp5dt. That first beta was less than 100 2 days later, so we knew it was doomed.