Closest I get is with firefox... at least every newline (not crlf) starts a new row. Safari and Chrome paste all lines of data into A1.
But, even in firefox, the CSV data fills only the first column... like Excel, but Excel gives me a formatting option, where I can tell it the data is separated by commas.
And, no, I can't put it into a CSV file, as Excel doesn't like those coming from Mac/Unix, as they use newlines, rather than the CRLF's DOS uses (and defaults to thinking spaces are the data separators rather than commas). I've used the "paste" in Excel for years to overcome this problem, but Excel Online won't allow me to tell it the format of the pasted data as Excel does.
There is a menu function "Paste Formatting", but that is disabled, as Mac doesn't allow web pages direct access to the clipboard (the user must paste).