Why this obsession with "all words must be known"? People are perfectly capable to understand the core of the message even if it contains unknown words. It happ

Why this obsession with "all words must be known"? People are perfectly capable to understand the core of the message even if it contains unknown words. It happens not every time, it doesn't happen for example when each one of the words is unknown, but the message: > "This message has been deleted from the mail server, but Outlook still has it in its temporary cache on this device. You can copy the message contents, or discard it from the cache, at which point it will be permanently deleted." can be understood. Even if the first sentence looks like a technical garbage, the second gives the clear instructions. And I don't believe that the first sentence is a complete nonsense to a layman. It can be understood as "message is halfway through the process of the deletion".