Good to know everything looks the same, thanks for all the tests.
Your other samples are probably from a higher quality source or are of higher resolution. Most JAV studios aren't recognized for producing visually high quality DVDs.
And the picture get stretched quite a bit if you consider that it's actually only 354x478 since there's 2 next to each others which is about 12 times smaller than full HD.
Also, your TV can't display the image in 1920x540 and still keep the proper aspect ratio so it most likely interlace the video or something like that(not sure how that works though since half the lines are polarized for only one eye. Unless the TV can change the polarization at will) by cutting half of the vertical resolution of the source. I haven't managed to find detailed information about the process so I'm not 100% sure of what I just said though, but it's the most logical explanation I can think of. That means it stretches the picture from 354x239 to 1920x540 which is also about 12 times the original.