This is pretty bad advice. Any workplace will have a fixed way of doing things that are suitable for their legacy code and existing practices. Not to mention most places don't really let you extend over to other areas. There's a big difference between dabbling in some aspect of development as part of a job and handling it yourself from start to finish on your own.

Some of my biggest growths as a developer has been doing things on my own that businesses aren't going to pay someone to look into.