A list of local vulgar simplifications does not seem sufficient evidence for encoding. At the very least I would expect to see evidence of the submitted character in actual textual use.

It is difficult to preserve such characters in written materials. They are the products of historical times. They only circulate in specific periods and regions, and will disappear with the process of standardization. They were usually used in daily writing, such as slogans, ground or wall drawings, etc. with the change of buildings, the carrier of such characters will also disappear. Documents can preserve this kind of characters occasionally, but the usage of them is difficult to rediscovered.

In Andrew's opinion, does 《宋元以来俗字谱》seem reliable enough? I don't think the comment is reasonable. Besides, all other corresponding relationships in the evidence is clear and right.
For example,赣 and 㶥