Thanks for the report. Depending on the context and where it was pasted from, Findings will create the paragraph type that corresponds to what’s on the pasteboard. I will check as there might be a bug where it does not correctly paste plain text and does not correctly match the current paragraph style.
I’ll let you know if I find a bug there and fix it, but in the meantime, you can use the menu Edit > Paste and Match Style. Let me know if that helps.