Yes exactly, content module works just fine.
I wonder if this might be related to “BUGFIX: Additional styles for modules loaded after Neos”, although in the corresponding comment there is no noticeable difference in how the stylesheet is included. Could it be possible that the f:uri viewhelper behaves differently?
if it’s of any help the problem, from a quick test, seems to generate in file: TYPO3.Neos\Resources\Private\Templates\Backend\Module\Index.html (lines 9).
In content editing the same snippet is called from file TYPO3.Neos\Resources\Private\Templates\TypoScriptObjects\NeosBackendHeaderData.html (line 11) instead, and the ways the link is generated are different: