> ... including the puncutation ..
FYI only: apart from the mere presence of OpenType Fractions ('frac') there is no standard between fonts in what the feature actually does. The "cheapest" option is to only replace "1/4", "1/2", and "3/4" with the proper (existing) characters "¼", "½", "¾".
With a bit more effort from the font creator, you can use any series of numbers to create fractions – but what it does depends on how the font creator implemented this. Some start off by changing all digits to superior, and then change (now superior) digits after a slash or fraction slash to subscript digits. This will always change all digits in selected text!
Others do a bit of intelligent lookahead and only change digits before and after a slash, but that still causes problems if you apply Fractions to a date notation such as "04/24/2020" ...
There is no consistency either in what characters are supported by the feature. Usually, and most often, it's just the digits; but as you found, Myriad Pro also supports decimal notation: "3.14159/4" will superscript the '.' as well, while Times New Roman will not.
Ultimately, what works depends entirely on the font. And indeed this should only be applied to what you want to fractionalize.