I also saw that interview, then out of curiosity I tried to find any evidence of this. There are some fan sites with ostensibly original X-Files scripts out there[1]. Looking through some written by Carter[2], I wonder if this is apocryphal, or if he was messing with her a bit.
Just scroll through and look. In almost every paragraph or dialogue block, the last line ends very close to the right margin. Pretty much the only places that doesn't happen is when there's a single short line of dialogue by itself, meaning it doesn't wrap to a second line.
Looking through scripts on Boggsfiles, it's much more inconsistent, but it does happen, and perhaps more frequently in the later seasons. Here's one, from season 9; take a look at page 10 (page 13 in the PDF) for example, but it really happens throughout.
Hah! I was wondering if it was maybe something he started doing over time and should have looked more at the later seasons I guess. It's comforting that it's not just a fun story.
[1]: https://www.boggsfiles.com/x-files-scripts-by-season/season-... [2]: https://drive.google.com/file/d/1BQbfRmeq3FsajjYcEuqDHv0kf2B...