Please share how, because I've never heard this. The brake actuating rod goes straight through the booster, so unless that breaks or bends, I don't understand how.
A broken diaphragm means loss of boost assist, resulting in hard to stop. If somehow he got more air assist than expected due to some other failure, this shouldn't affect pedal travel.
I would certainly bleed first to get a firm pedal at engine off before replacing the booster (unless its failure can be identified).

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Prost!