I've never heard of a sieze wreaking a crank.

The bike could be fine and you may have jst been very lucky, I've seen one minor sieze (Dave Reynolds racing with DP) when there was no piston damage, both rings still free. But that was a 4 point sieze so there was a issue with something still.
Other than that every one I've seen had a level of piston damage.
For the sake of about $2 (that's if you do replace the base gasket) I'd always check.
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