I wouldn't exactly say that, but I guess its "lucky". I'd say their bond caused it still. She took a liking to Tama and it activated the mode. She didn't interact with Momo directly while he was being executed, which may explain why it didn't happen there.
We still don't even have an explanation for why the Beast Pirates didn't tell the Big Mom Pirates about the secret entrance. Queen was literally surprised they didn't arrive yet so it wasn't intentional