What is there to fix? The colon has a special meaning to the Windows NTFS driver - if you use that in a filename then that file is inaccessible with that driver.
If you put a null or forward slash in a filename on an ext2 filesystem then that file becomes inaccessible on linux, should they somehow "fix" that?
Of course, they should. It may be hard to fix it, too hard for it to be worth the disruption in stability, but it is a design error that breaks user expectations and can cause severe issues when interoperating with other filesystems.
And with NTFS, this is much more severe than your example with ext2.
For one, ext2 is a niche filesystem at this point, users practically never interact with an ext2 filesystem. It's not the main filesystem used on Linux.
And secondly, as a user, I have created files with '/', ':', '*', '?', '"', '<' or '>' in the name ('\' and '|' are also forbidden on Windows, but I admittedly have not yet needed those AFAIK).
Not being able to use these characters limits the ways I can express myself in what a file contains.
For example, I've had to rename a list with different levels of grouping from
"List of members: City > Lastname > Firstname.pdf"
to
"List of members - City, Lastname, Firstname.pdf".
And I'm still not convinced the recipients of that file actually understood that the levels of grouping were listed in the filename in the order from biggest to smallest grouping level.
Presumably, fsck-ing the NTFS volume (or the Windows equivalent) should canonicalize the colon into some escaped/mangled form, since it isn't valid for it to be there in the filename.
If you put a null or forward slash in a filename on an ext2 filesystem then that file becomes inaccessible on linux, should they somehow "fix" that?