That's terrible advice, in my view.
In your job you should always do what is the most useful and productive use of your time.
As a tech lead/manager your role is to manage/lead and your time is extremely valuable. In addition, your job as a manager is to allocate resources efficiently.
A small feature is a good task for a junior engineer. It helps them grow and their time costs less than yours.
Bug fixes should be the job of whoever knows the relevant part of the code best, which is unlikely to be you if you're a manager but even if it is you should aim to train and mentor others to acquire the technical expertise.