I ran into this as well, so after working out the relevant tables in the WSUS database, I used the following SQL
use SUSDB;
select CT.FullDomainName, CONCAT(STR(CTD.OSMajorVersion,2,0), STR(CTD.OSMinorVersion,2,0), STR(CTD.OSBuildNumber,6,0)), CTD.ClientVersion, CT.LastReportedStatusTime from tbComputertarget CT LEFT JOIN tbComputerTargetDetail CTD ON CT.TargetID=CTD.TargetID ORDER BY CTD.OSBuildNumber;
Sample bit of output with names removed - shows how 21H2 (19044) shows against the client version.
10 0 19044 10.0.19041.1320 2022-01-14 14:11:27.467
10 0 19044 10.0.19041.1320 2022-01-15 16:13:33.963
I would have used CONCAT_WS to get . in the OS build version but it wasn't in the SMSS version I was using.
The build numbers don't show in the "Additional Details" section in the WSUS console.
Possibly the Mobile Operator field could be updated with this information using an SQL script, so it was visible in the console..
Hope this helps,