Orcas in the form of clicking sounds and humpback whales, who can sing in ranges as high as 8000Hz.
However, these calls are produced via an entirely different vocalization method.
However, these calls are produced via an entirely different vocalization method.
See, specifically, the sub-heading on Odontocetes — literally, "toothed whale".
You appear to be operating with the category that "whale" is wholly and exhaustively synonymous with "baleen whale". You're wrong.
"They [whales] are an informal grouping within the infraorder Cetacea, usually excluding dolphins and porpoises. "
I guess I find the blue whale + fin whale hypothesis a little odd (why would the hybrid have a call that's higher in frequency than either of the original species'?), but I don't have the expertise to comment on it.
I don't think this is right. The hybrid with a lion father and tiger mother is the huge one, but the father comes first in the name of the hybrid; tigons (male tiger / female lion) aren't so large.
The reason for the difference is that male lions brand their offspring's DNA with the urge to grow large, while female lions counter with the opposite urge. For a lion/lion pairing, this balances out, but tigers don't have the same war between the sexes going on, and the maternal tiger genetic contribution is defenseless against the paternal lion one.
Humans, by the way, do something similar: the same genetic defect causes "Prader-Willi syndrome" if it came from the father, and "Angelman syndrome" if it came from the mother.