There are TV attributes that can make scanlines less visible sure (I'm sure CRTs had different levels of light bleed too for example), but there isn't a PAL/NTSC difference between scanlines except being less noticeably with PAL because of the slightly higher resolution (288 lines vs 240).
I think you would still notice them on any SD CRT if you were looking for them.
Edit: looking at how this started, I think it might be my mistake with a bit of misnomer that 400p has "scanlines", which I think only refers to the 480i/240p hack (obviously there's still a gap between lines even in other modes, but in 240p I think every other line is actually blank? I'm not an expert on this).