We have no idea whether the signal had a pattern because the only recording we have of it consists of averages over 10-second samples, so any modulation <10s (or patterns larger than the 72s recording) would have been lost. It could have been an AM broadcast of a herd of circus elephants playing the William Tell Overture for all we know.

True. That's why I hedged with "seems to". Our only measurement of it is consistent with it being a single pulse