The use of `` and '' comes from the typewriter days. You’ll see it particularly with professional authors who have been writing for print since then.

See https://en.wikipedia.org/wiki/Grave_accent#As_surrogate_of_a...

US QWERTY keyboards like the author is almost certainly using have the backtick above the Tab key, shared with ~, and it’s commonly used in programming.

I blame Microsoft, as it was their software where I was first introduced to "smart" quotes using the extending characters/glyphs of fonts. I can also tell when importing someone's data that was copy/pasted from an Office type program with its auto"correcting" to smart typography.

The backtick? That's generally the non-shift character on the "tilde key", generally right under the escape key. It's on most physical keyboards.