Hmmm. "Apparently", indeed.
As a cynic, how do we know those saying they voted Leave and regret it actually voted Leave at all? I mean, unless you(*) can get access to their specific, actual ballot papers, and the electoral lists with reference numbers, and don't mind committing several serious criminal offences in the process, they can claim to have voted anything and it can't be challenged.
It is, however, not a bad way to undermine credibility.
Maybe I voted Remain but now wish I hadn't.
(*) A generic "you", not you personally, Phage.