They may have tried. Most of the services used to wipe posts and comments were ineffective on content more than a couple years old because Reddit wouldn’t report that the content existed.
I couldn’t verify this directly either, but I know some users had also claimed that, after Reddit started catching on to what people were doing, they’d keep the content anyways, un-edited, and just hide it from view on your account so you wouldn’t know it was still there unless you went back to find the original posts, which most people wouldn’t know where to find.
During the whole debacle, I wiped my content but kept my account in the hopes that they’d backtrack on their decisions. Shortly after joining Lemmy, I googled a question on Reddit and saw that I had an inbox message, someone replying to a comment that I had made years before which, surprise, was not deleted. Clicking on my comment history on my profile showed nothing, but the message was still there in the thread under my name.