Exchange conditions and actions reference - DLP policy

I have a question about this page here: Microsoft Learn DLP exchange conditions and actions 

Under "Actions for DLP policies". There is an action parameter listed called "ModifySubject". There is further detail around this parameter here: Microsoft Learn ModifySubject  

However, something that is not clear to me is its logic. Let's say I use the 'ReplaceStrategy' of Prepend.

Will the replacement text be prepended regardless of there being any pattern matches? I.e

If the subject line of an email doesn't include the word 'apples', and the ModifySubject pattern is looking for 'apples' and it is not found will the replacement text specified still get prepended even though no pattern was matched?

It's my belief that it will not prepend anything unless there has been a pattern match (thus removing some content from the subject line) before pretending your desired content. But I hope to be wrong and it prepends the replacement text specfided regardless of a pattern match or not.