Some personal experience, some anecdotes, some assumption. Nearly every time I've read a job posting using similar language, when I've been able to actually talk to the developers there I find out that yep: it's long hours expected.

There's specific words, like "self-motivated" or "willing to learn deeply" to convey the ideas you're talking about, without meaning working extra hours. But when a job posting uses the vaguer "passion", "grit", or similar hustle-y words, it's just a red flag to me that they're being non-specific - they probably have a reason.