Sorry but that is terrible advice wobbliscott.
Cheap poorly fitting hex keys keep workshops in business.
I’ve had cheap keys appear in sets from the likes of Halfords that have slop from new in bolts that quality hexes fit in snuggly.
If you get good ones then fair enough but to assume all that are of a certain material are made to the same tolerance is foolish.
Hex keys also wear – in a workshop environment we would get replace our 4 and 5s at least once a year -you could clearly see the discolouration where the surface finish had worn down-on measuring with a mic there was measurable wear -which when your working on thousands of pounds of customers bike is not cool.