Earlier quoted context omitted.
this is patently not true. maybe titanium is gummy enough to give one trouble? but any steel that isn't brittle enough to shatter when you look at it is going to be trivial to cut with an abrasive disk and a battery powered grinder. if the chain is 1/2" instead of 1/4", it will take an extra minute maybe.
And, frankly, who’s going to stop a guy with an angle grinder from stealing a bike that isn’t theirs?
I don't think taking a photo will have any actionable follow-up—I have no way of following up to see if someone reports to see anyone has reported a stolen bike in the area—but might make a thief decide to go find a different target, while not being a major issue if you're the actual owner.
As a healthy, medium-large guy who's okay at de-escalation, I live in the assumption that no one will try to hurt me for interfering. I'll probably learn better one day.