I don't pretend to know what he has / doesn't have - not fair for me to give any more details about him as it might identify him, albeit he is very experienced.
There was a clarification in 2018 I believe on this (this doc was amended then) also.
Firstly I believe you don't need a medical to be an SFE.
My reasoning (without talking to the examiner) is that the doc says that you can have an SFE without a medical (with a temporary examiner certificate SRG1100a) as part of 8.5.1 as quoted above. That wont be open to everyone - depends whether they can be an SFE.
It says any examiner can sign a revalidation - see 12.3 of that doc which is an extract from Part FCL:
3) If an examiner (e.g. TRE, SFE, CRE, etc) has satisfied himself/herself that the requirements
above have been fulfilled, they may revalidate the rating
So therefore, he can sign for revalidation without a medical via SFE.