Why was this migrated? There are other PGP/GnuPG question in InformationSecurity.SE
Because your question was on the basic use of the tool. It wasn't about security, but about tech support (of an encryption tool).
"How to run command X?" tends to be more on topic at SuperUser.
We do not expect everyone to understand the subtleties between the different Stacks, so migration is normal and common.