None of the FCS in that paper are the same: RRAR, RTAR, RSVR, RVRR, RSGR, RRSRR, RRSR, RAKR, RAHR, RRKRR. There's clearly an awful lot of functional sequences

None of the FCS in that paper are the same: RRAR, RTAR, RSVR, RVRR, RSGR, RRSRR, RRSR, RAKR, RAHR, RRKRR. There's clearly an awful lot of functional sequences that we know of that produce an FCS and uniqueness there isn't special. You're right that I wrote sarbecoviruses when I meant beta-coronaviruses. We still don't know of any sarbecoviruses with an FCS, but MERS has an FCS and the bat beta-coronaviruses HKU4 and HKU5 have an FCS.