More accurately, it's tied for third place with C++.

That doesn’t mention PL/I, so it’s the competition for amateurs. https://www.cs.vu.nl/grammarware/browsable/os-pli-v2r3/:

    Summary
    Number of keywords: 310

PL/I made life ‘easier’ by not making keywords reserved, allowing you to use variable names that match the strings used to identify keywords, though, so you didn’t have to learn them all.

They’re certainly wrong about Scheme. They used MIT-Scheme to count keywords, when they should’ve used R5RS Scheme or newer. R5RS has 20 keywords + 4 if you add support for macros. With define-syntax you can define many special forms such as let, let* etc in a smaller language so may be the actual number is much smaller!

They don't say what version of Swift they're counting, but I count 96 keywords on the documentation page they link to, which would move it above C++ into 3rd place.

oh wow, smalltalk has only 6 keywords. that's really... small :).