Ok, it looks like the standard pre-approval notification email, and NOT the actual invite to schedule the biometrics which allegedly has a 10-day expiry window.
I cannot compare to my own notification email because I never received one. It appears SEF sends emails to the lawyer’s email address ONLY, and none to the applicant’s email.
The information on the biometrics scheduling is posted on this thread, where you can see it stopped around May 2021: