I so want to agree with your conclusion. While I agree cable/Internet providers are behaving in a way that rips consumers off, I think in this case you might be attributing this the wrong way.
Roku provides a subscription activation code and gets back a response from the content provider.
HSI provides an account holder login confirmation along with confirming that the content provider is part of the service their customer subscribes to.
Once you are confirmed as authorized, the choice to cut off the premium content access is largely in the hands of the content provider.
Each of the channels you stated also have smart phone apps available. I would recommend trying it on the smart phone and confirm the restriction of 3-5 episodes does not also take place on the smart phone app.
My best guess is that all three channels are using similar software for trying to combat account sharing. Both HGTV and Food Network are owned by Discovery, Inc. and National Geographic is owned by Disney Corp. In the case of Disney, their hate for account sharing is documented in a couple places including this Wired article:
https://www.wired.com/story/disney-streaming-account-sharing/
One possible reason you are seeing this problem now is if you have been sharing account information with someone else back in Florida. It might be possible if you share the account with someone in the same state that you can fly below the radar of their anti-sharing system. If it is the case that is what is triggering the problem, then the best solution might be to stop sharing your account.
If you aren't sharing your account, then there may be something else that is triggering the content provider restriction. This might be related to HSI's network behaving in a way the provider didn't take into account correctly. But I don't think it is something that HSI would have done intentionally. You may want to contact each of the content providers directly to get assistance on why your Roku authentication state is being halted prematurely. it is possible they will tell you to contact your service provider. This doesn't mean HSI is to blame but does mean from a content provider's perspective their direct customer is the provider instead of you. If that is the case, try to calmly explain again to HSI support what the issue is. If they don't seem to understand, ask to have the issue escalated to a supervisor or tier 2 support person. They should hopefully eventually be able to open a ticket with the content provider on your behalf to get the issue resolved.
Roku, for their part, is trying to help address this type of situation by giving the option to subscribe to premium channels through Roku's own Roku Channel. This would allow you to stop treating companies like HSI as a cable company and only as an Internet provider. This would eliminate middle man effect of HSI misunderstanding the situation and pointing the finger at Roku. But at the current time the 3 content providers you listed aren't on the list of 48 premium content providers the Roku Channel provides. Also, the content providers will still reserve the right to enforce their terms of service against account sharing even if that sometimes means frustrating some customers due to false positives in detection.
