new to this forum. Great to meet everyone here.

Background Info:
Sponsor : wife
Applicants : myself + 16 y.o son from previous marriage.
My question is about my son's renewal in 2 yrs time .... and there is a slight techinical problem due to timing issue ..... so, please do bear with me.
He is now 16 y.o. living here on dependent visa via my relationship with my BC wife, his visa will be expired on 25th Apr 2021.
He will turn 18 years old on 13th Mar 2021.
I understand that if I apply his FLR(M) renewal after his 18th birthday, he will need B1 english test.
Now, If I apply his renewal by submiting his on-line form from 2nd Mar 2021 (thats when he fulfils 30 mths residence) AND before 13th Mar 2021 of his 18th birthday, he is technically still a minor and doesnt need B1 test. BUT, if appointment for submission documents is after 13th Mar 2021, will HO request B1 english test for my son when we are at the centre?
TIA.