But for pathtracing this does not make any sense.
This is partially true imho :- )
It's true for anti-aliasing yes (with exception of hdr 'jaggies', which look smoother if glow and tonemapping is applied at higher-res and then down-sampled, or, Corona's "internal resolution".
But it's less so for detail. At higher resolution, shadow and texture detail (and effects, like bump/normal) converges to higher detail, shadows are bit more precise and textures are better filtered. When downsampling, this detail is preserved compared to rendering at native res.
Also, post-production is much less destructive at higher resolution, you don't have to be pixel-perfect with masking and worry so much about introducing additional noise and loss of detail.
Displays are getting bigger, almost every laptop on market is 3200 to 3840px. Lot of web imagery will start to be at this resolution soon (it's not size problem, because even currently, it's better to upload high-res but very compressed, then small res but good compression, same visual effect).
If you can, go high-res, it always looks better. Stuff I do gets always printed so for me it's not even choice.