The big problem with his argument against PHP being a template engine is that it hasn't been developed with that in mind for quite some time. I think it's just a legacy feature to just echo out anything after a closing php tag and before a new open tag that WordPress still enjoys.
I'm of the opinion that anyone now who calls PHP a "template engine" hasn't actually looked at it since 2001.
I'd compare it more to the way you can use Ruby as its own template language. I don't think I'd really build a PHP app in 2022 the way I would have built it in 2002, but I'd be okay with using "pure PHP" templates, assuming I trusted whoever was creating the templates not to blatantly abuse it. (I know that could be a big assumption in some contexts…)
I'm of the opinion that anyone now who calls PHP a "template engine" hasn't actually looked at it since 2001.