Why not positional variation?

[dashstofsk]

it would appear strange to use two different versions of the same character this way.

My hypothesis is that the alphabet is an invented one and that the authors intended that no-one should ever be able to read the manuscript. And because of this the authors were not obliged to have to follow any particular standard, and hence no obligation to use m in place of r on every occasion. At the end of a line they had a choice to use one or the other. I see that the authors had similar choices with other characters throughout the text. Earlier, in

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I gave my view that iin and in words were the same. The authors minds were sometimes in single stroke mode, and at other times in double stroke mode. Similarly with r and m. Sometimes they wanted to add the downswing, and at other times not to do so.