I suppose. But who reads the sort of banal statements like "my parents raised me to work hard and treat others with respect" and think "hmmm, that sounds familiar. Oh, I know. Michelle Obama said the same thing eight years ago!" You have to be a super-fan of Mrs Obama to recall her specific wording of those generic sentiments. So if someone purposely slipped them in, I could see them making it past through the process.
The don't have to. There's software available that campaigns feed speeches into specifically to locate similarities and to avoid gaffs like this. It was entirely preventable but who ever was working with Mrs. Trump on the speech didn't do it.