Not sure where you heard this. If your bike is geared appropriately for the terrain you’re riding, you’ll use all cassette cogs.
I have a 32 front ring, 10-50 cassette. I use the 50 tooth quite a bit for sustained climbs in the Colorado mountains.
If you are looking for different setups for your bike, considering picking the cassette, and adjusting the chain rings, vs having two cassettes. Cheaper and easier IMO to go with this approach.