This documentation is certainly a good start, but lacks much guidance on setting up and running rSpamd...
If I can give my opinion:
1 - certain things are assumed in the guide that are not enough to do a "fresh" install for someone who isn't already well versed in Linux.
For this reason I would recommend making a more precise and detailed "HOW TO" guide, like the ones you find on HOWTOFORGE.COM
2 - there is no indication of how to interpret rSpamd replies and how they affect SmarterMail in order to then be able to do some fine tuning.
3 - there is no indication of what it means to add the scores of rSpamd to those of the other filters already configured in SmarterMail.
Could it happen that a "good" email that has always had a low spam score in the SpamAssassin filter, by activating rSpamd, also receives a low score from the latter, but adding the two scores together SmarterMail erroneously considers this email as SPAM?
4 - There are no indications on the functioning and configuration of the self-learning function (see image below)