It's addressed in the original post:

Now, if you live in an older neighborhood, you are probably not the only one on the block with this problem, so it's worth putting things into perspective. Also, if you are powering this off of the car's 12V or USB, this is somewhat remedied by the fact that the power will be cut off once you are parked (and so the RF rely will be inactive). However, things like sentry mode, software updates, or even just checking on your car in the app would wake it up and leave you exposed, so it's probably not something you should count on.

Ideally, you would use a relay kit that uses the more secure rolling code system but can still be understood by HomeLink. Most of these systems uses the same chip/algorithm, so it's just a matter of finding something that is in HomeLink's database. It probably exists, but may take some trial and error to find one, so if you found something that works, please do leave a link.

So sort of? It's not as much as a risk as you may think, because this only works when the car is parked AND the car is awake.

That being said, I do think it's not ideal and am trying to find another relay that uses rolling code. Part of the reason I wrote this is to hopefully generate some interest/discussion in this technique and crowd source finding/testing better parts.

I have this one on order, for example: https://www.amazon.com/Solidremote-12V-Universal-2-Channel-Transmitters/dp/B01JGDV8UM/ I have updated the post to include this link, but until it arrives, there is no way to tell if it works with HomeLink.

Another slightly more expensive option is to use a standalone receiver/controller product like this one: https://www.amazon.com/Genie-Company-ALKT1-R-Smartphone-Anywhere/dp/B016QB7K5O/ Same thing though, need to check for HomeLink compatibility and voltage requirements to see if I can power it with the car. It'd probably also consume more power than I would like/need it to.

Also, as I mentioned at the end, there are other things you could do with this approach where security matters less (controlling a light, using the on-screen button to trigger other automation workflow, etc).