+ in Field Names doesn't work always

Problem/Motivation

so it works only when `Disable saving of submissions` is enabled in Webform settings (and method validateFormCustomSubmissions() is used):

https://git.drupalcode.org/project/spamaway/-/blob/2.0.0/src/Plugin/Webf...
https://git.drupalcode.org/project/spamaway/-/blob/2.0.0/src/Plugin/Webf...
https://git.drupalcode.org/project/spamaway/-/blob/2.0.0/src/Plugin/Webf...

otherwise, `+` doesn't work, and we have null as the field's value.

But Field Names help text says `...YOU CAN ALSO ADD 'IP' TO CHECK ON IP ADDRESS AND COMBINE FIELDS USING A + SEPERATOR. EX: FIELD_A,FIELD_B+FIELD_C,FIELD_D+IP`