I agree, that advice is more for managers than tech leads. A mistake I've seen orgs make often is promoting their best developers into role where they don't code. A tech lead that doesn't code is a manager.
Where I worked, as a lead I was probably doing up to 50% individual contribution and the rest "management". But I have seen new leads in the same role do 150% individual contribution, and then let their team down on leadership tasks because they've let themselves become swamped. This is a very common error for any newcomer to a job that involves leading other people (which OP specifically says is their role).
I don't think it's an error to put a coder in a position of leading others; it's just that being a productive coder is a weak predictor of being a good lead— you have to look at other markers. Having that kind of "on-the-ground" understanding can be a great strength that can't be had any other way.