Yes. this is intended behavior. Activating (or deactivating) doesn't nullify the trial.
While this probably has no net effect in 'real life' I'm going to ask the question out of curiosity.
When I deactivate I notice that I am back on my trial period (assuming it has not expired). Is this the intended functionality?
Yes. this is intended behavior. Activating (or deactivating) doesn't nullify the trial.