> I have met many programmers that don’t like to code in their spare time, and that has reliably revealed them to be sub-par developers.

I dunno. When I spend 8 hours a day coding (paid), spending another 2-4 working on my own stuff isn't all that appealing. I mean, I want to do other things with my life than just write code. If that makes me a shoddy developer so be it.

When I'm not busy on paid work I do explore new technologies and techniques. Perhaps this is what the author is refering to? However I still consider this to be "work", as it's a way to shore up my skills. It's unpaid but it makes my skillset and my time more valuable.