Mimemapping without mimetype

When importing some mappings from my RISC PC, the one in the form did not work:
– PCTk 1b1 .dtm .gtk .gt2 .aon ….

Then I remembered some comments I made in !DigitalCD.Docs.MimeTypes file:
- the use of “-” which denotes the lack of mimetype is not supported on all versions of RISC OS and a fake mimetype should be used instead.
- on non-Select machines the process stops at the first match even if it’s a wilcarded one so wildcarded mappings should be placed at the end of the file.
- Mac filetypes (enclosed between "") should be removed from the file when the version of RISC OS does not support them.

I wonder if all those limitations are still true in OS 5.23?

Another difference with my RISC PC on that PCTk line. I list in there more than 20 PC extensions covering various PC trackers formats. On OS 5.23 I need to split the line in two or the last ones are not taken into account.