Great, you've been digging in the code details
Yes, you are right in eventform0.php and eventreport.php the nom and nos parameters (nom => number of days before event to send a reminder email and nos => idem for SMS) are not added to the $evt array before calling the function makeE. However, the nom and nos parameters are only used by the makeE function if the template (2nd parameter in makeE function) contains a '6' and - and this is important - if a '6' is present in the last parameter 'show'.
In both cases, eventform0.php and eventreport.php, the last parameter of the makeE call does NOT contain a '6'! So in these cases the makeE function will never use the nom and nos parameters and therefore these parameters need not be present in the $evt array.
So it is intentional that in the eventform0.php and eventreport.php code the nom and nos parameters are not present in the $evt array.
(If makeE would use these parameters while they are not present, a PHP warning would be produced, which is not the case.)