It depends on the provider. They can choose what the logo means.

Ps I looked it up, it can show it if the cell has 5G even if you're not connected to that at the moment, not if the network has it somewhere.

But each provider makes different choices. They have like 4 options to choose from.

You can use a network monitor app (or the built in one but it's a bit technical) to see what you're really connected to.