This was actually mentioned in another bug report by @chDVRuser and I can confirm I am seeing the same result.
Summary: All m3u sources without corresponding xmltv URL will combine on the WebUI Live TV Guide when selecting any one source without an xmltv link.
I’ve actually noticed that too, but I hadn’t gotten around to determining if it was just something I was doing wrong. But yes, I also see the issue mentioned. I can confirm that all my .m3u sources with no corresponding xmltv link do combine on the Live TV Guide.
This was also reported last year: