RFCs are often useful guidelines, but don't get too hung up on them. There are always side effects. eg resource usage, interaction effects (cache priming), etc.

[Edit:] > The point is that GET is not supposed to change the information stored on the server side.

The RFCs for HTTP USAGE are guidelines that are less about utility and more of an interoperability dream that was never realized. There's nothing sancrosanct about them. There have been DECADES of usage contrary (eg medical, gamedev, advertising, ERP, etc). At some point people realize it's bikeshedding issue that's more trouble than it's worth.