Most mathematicians, engineers, and scientists don’t use the asterisk symbol for multiplication. Most don’t write any symbol as it’s implicit. If they do use a symbol they would use a dot or x symbol (though never an actual x). In mathematics, the asterisk is mostly only used to represent convolutions.
Most common:
abc
Less common:
a • b • c
a × b × c
Never:
a * b * c
While to most people this doesn’t really matter (and should feel free using * for multiplication). It shows someone with minimal formal experience in mathematics using this formula
Can confirm it is a font substitution issue. When I open the PDF a different font is used (note the very distinctive “r”) which has much better (but not great) kerning.