403(b) correction when an employee signed up

[Lori H]

  new hire entered safe harbor 403(b) 8/1/17 and filled out the salary redirection form in August for 6%. He failed to enroll in the plan online and plan sponsor inadvertently filed his form without setting him up (it was an oversight on sponsors part but they were waiting on him to enroll before they added his contribution amount into ADP). He’s now requesting that they take the extra two months out of his next check and would like the enhanced SH match (100% up to 6%). 

I am of the opinion the sponsor has to make a QNEC of 25% of what his deferral would have been along with SH match and any earnings under SCP.    Is this the proper correction?