"You were the one who tried to destroy Yoshi with that mutagen"

[neatoman]

Wasn't kind of a careless revision to the origin story? If Shredder intended to kill Hamato Yoshi there would have been plenty of less dangerous ways to do it, what he actually did was an incredibly bad idea regardless of wheter or not he knew what was going to happen. If he didn't know what the mutagen was, then pouring an alien chemical down a storm drain could have done way more harm to city than he expected. If he did know what the effects then pouring down a sewer would also be a bad idea, then something else could mutate and cause problems for him, which is exactly what happened...