There's "vintage" and there's simply "older". If a design hasn't changed in 35+ years, how exactly is being 35 years old, vs 25, vs 15, vs new-in-box in any way different (apart from wear and tear on the controls and switches)? If it was the case that any of these were made using parts that have changed in quality over the years, or simply cannot be gotten anymore (e.g., some germanium transistors, pots with a very idiosyncratic taper), that would be one thing. If it was the case that there was component changes that resulted in different noise specs (e.g., I've found that in some of the Behringer Boss-clone pedals I have, they opted to use lower-power chips, at the expense of more noise), or different headroom (e.g., when Boss switched from the MN3005 fed a 9V supply to the MN3205, fed 5V, in the later-issue DM-2 pedals), that would be one thing.
But, normally, the term "vintage" is used to refer to a period of production when there was something distinctive about what was produced, and in this instance there simply ISN'T. A BF-2 is a BF-2 is a BF-2. I don't care if it was made in Japan, Cambodia, Eritrea or a Scarborough high-school shop class, because the design has not changed since the first ones. Yes, a survey of gutshots shows that they changed the model of trimmers used, and the part number of the chip used for the LFO changed (though it remained a low power FET op-amp), but that was it.
When Boss decided that there was greater long-term relilability of the trimpot settings using newer chips, they dropped the CE-2 model in 1983, and switched to the CE-3, et al. design such that nothing changed about the CE-2 (a very nice chorus sound, I might add) as a function of where it was made.
The NS-2 was first introduced in late 1987. Nothing has changed about the design in the subsequent 30 years. Boss uses a semi-proprietary chip (i.e., you can get them, but it is REALLY hard, and likely involves a trip to the Akihibara or very good connections). The CS-3 also uses a hard-to-get dbx chip. Boss doesn't embark on a product unless they can assure a steady and plentiful supply of the components. Often they get them made specially for them, but then they make/sell so many pedals, they can afford it.
The magic of the internet is that perceptions or opinions about something in one context, are haphazardly and superstitiously applied to another where they have no relevance. Is there a difference between Telecasters made in the USA vs Mexico vs Korea vs China? Yeah, probably. But those things are made of wood - a highly variable material whose treatment requires close attention - and are fundamentally mechanical devices, with some electronics thrown in for good measure. If a pedal is made using the identical components that I can order from Digikey, Mouser, Jameco, Farnell, Maplin, Tayda, and dozens of other electronic component distributors, and the same boards and layouts, using the same mass-produced enclosures, then how the heck does country of manufacture make any difference whatsoever? What we see is that a factor which is legitimately pertinent in one context (guitars) is presumed to be more broadly pertinent, simply because, well... you know...because...I read it somewhere.