[Edited on 23/04/2021] This is fixed ! … Along with new SDK release 0.12.0, it seems there is a new navigation bar used for online documentation now and it renders Maths correctly. At list on the edge browser that I tested today.
[Edited on 10/4/2021] The quick summary is that I converted the page to a PDF in case you want to read it and put it here for you to download. Better option is to download and install SDK from developer mode, and use documentation that comes with it. It seems recent SDK has similar release note version as online version, but the formulas are rendered correctly in the browser from local copy.
Long version of story is that I think I figure out why we can’t see the correct format of the page. When I tried to debug the page through Edge DevTool, I have noticed CSS formatting, applied to the page, related to navigation panels at right hand and left hand side of the page, showing topics and sections of SDK, override the original CSS which is responsible for rendering the formula. Original writer of the SDK document , has used MathJax https://www.mathjax.org to format the formula if you look at the source. But whoever put it in a wrapper for nice formatting and provide sections and topic on both sides of the page , screwed original CSS format. I managed to remove a few tags in the HTML and stop browser to load side panels, temporarily, while it was in the debug mode of Edge, and save the page in a PDF. That is what I shared with you in the link above. However, this issue exist on all the pages of SDK and there are many formulas in other part of SDK which are impacted.
I really hope that MS/Asobo fix that, because reading the formula is not a simple task without correct formatter, and it should be a quick fix from their side.