Not, not really. You probably find this character in a column of the files list.
Have a look at the definition for "value" and you will probably see something
which means that the
\\ are defined as separating characters but you could just as well take any other character. Foobar, I think, takes the semicolon as separator
The point I try to make: as there as so few players that actually the real multi-value fields, there are some players that interpret special characters in a single-value field as separator and display the items separated like that as individual items.
I know that e.g. WMP use the semicolon in ARTIST, GENRE, ALBUMARTIST and COMPOSER to create individual entries.
E.g. Stock; Aitken; Waterman would show an entry under A for Aitken, one under S for Stock and one under W for Waterman.
And all this without a multi-value field.
So it could be that there are other players around that do it like that.
And whatever the implementation would be: MP3tag can help you to set the right format.