The thieves around me seem to look past vintage road bikes in favor of more modern stuff. I used to ride past a couple of their camps and would glance to see if anything familiar had shown up, about 90% are mtbs. There's a lot of cheap BSO and low- to mid-range lbs bikes bought in the past 10yrs. Not too many skinny steel tubes.

I'll second a scratched up frame. That's been my go-to for my street-locked bikes.