How do you propose to do modular design without a templating system? While I only skimmed the article, it seems the author has it "right on." If you ever had to work with designers before, you'll immediately see the benefits for non-intrusive templating languages like FastTemplate, SmartTemplate, etc. over raw PHP.
If you have the luxury of not having to work with any designers then there is no need to separate "the PHP code" from the templates... no need for modularity.
In other words, like all OOP design, templating gives you the flexibility in a certain direction. If you don't need that flexibility, you don't need templating.
BTW, OOP does not slow PHP4 down significantly more than an associative array and a bunch of functions, because that's how PHP4 treats it (much to the headache of a lot of PHP programmers I might add). Of course, things will be even more optimized with PHP5.