The letter advises clubs that if they want to see the details of the case, they have to either tell the court that they’re respondents to the complaint or formally ally themselves with the answers that the league or the 3 promoted clubs have provided to the complaint. It’s very clear that the league are advising this is the only purported route to seeing the documents.
To me, the notable thing in the letter is that it does not advise clubs of any other potential route to seeing the documents - such as the route of formally associating themselves with the Hearts/Thistle position. However I’m not sure if, legally, that’s possible - perhaps some other legal minds can advise?
If it is, then Doncaster’s letter says “if you want to see these documents, you’ll have to ally yourselves with us in the case as a respondent” which is misleading and decidedly fishy. It coerces clubs into getting involved in a certain way just to be informed on the basics of a case that no doubt interests them greatly.
It probably doesn’t make a lot of difference to the case itself but it does seem like an attempt to make it ‘everybody Vs Thistle and Hearts’ and you can see why we’d dislike it.