I don't know why this seems the standard practice in the industry, but it really annoyed me when I realized a “15TB” LTO-7 tape has actually only 6TB real, “native” storage coz it assumes some average compression ratio.
Why is this acceptable? What if I use the tape to store incompressible data like video and images? Feels like intentional cheating.
When a company is spending >$20k on a tape system, the people in charge of buying it will talk to the sales people, tell them the use case, and get a more accurate estimate.
The fact that buyers may talk to salespeople is really not an excuse for the deceptive behavior.
"well, in our restaurant medium rare means well done and rare means medium rare, but that's okay our customers are well-paid professionals, they'll talk to waiters to get a more accurate picture"
Clothing manufactures also lie about the waist measurements of pants. (Go measure yours and see.)