I received from LF support the following reply:
This is as expected because when you try to create a document with field values assigned, actually the document will first be created, and then the template/fields are assigned. The error pops up in the first step.
This behavior cannot be modified since the actions to create the document and to set fields value are two different steps. LF Server processes the creation step and check the Folder Filter Expression, then it gives the warn. If LF Server don't check the Folder Filter Expression, user might not set the fields correctly during the creation, that might be a disaster.
A workaround is to create the document from other location, apply the template and fields, and then move the document to that folder.
Alternatively, you can use the following expression:
Entry.Creator = context ('username') OR (IS_GROUP_MEMBER('YourGroup') = 1 AND ( entry.type='folder' OR entryprop."YourFieldName" = 'YourValue'))
Which will allow the users to see the documents created by themselves.
You can also setup workflow to verify/correct/enforce/etc the related business restrictions.
Hope this could help.
Best regards,
Ignacio PdeA
BMB sal