Worse, generally. Car manufacturers are completely awful with privacy and also very bad at security.

this subscription involves a mobile plan and access to a backend service though

As they pointed out in your original post, it's not, "the subscription model...for something that you already paid & own." This isn't subscription seat warmers, it's paying for an additional service outside the car. You can argue it's too expensive, but without their internet connection and servers, these features wouldn't be possible.

Features like this really do require a subscription model. This isn’t enabling remote start by pressing a key on your fob. This is sending a request to a server, which connects to a cell tower to broadcast signal saying “turn on this car”. That stuff ain’t free. Someone has to pay AT&T for the data connection.

What BMW was (is?) doing is abhorrent. You’re buying a car with heated seats, and you have to subscribe to hit the button.

IMHO, It makes sense though. Piracy and open source are two approaches to attacking the enclosure of public (intellectual) space. Roads for cars are literally an enclosure of public space. The subscription model just extends from this logic.

Edit: These are also things that make sense because the car has to have cell service via a provider.

Then I should be able to self-host these softwares.

149 to send a ping to locate a car? For an API call to lock unlock? How many API calls are worth 149 per year? In which world?

Make the car cost £400 more, once, when it's bought first hand. That will cover any costs for the lifetime of the vehicle. There you go, chuck the subscription in the sea.

These are software features that need an open, secure API.

yeah, i agree. it costs them money so there's little to no incentive to run that stuff for free.
also the price is reasonable (about as much as a single Nano ec2 instance on aws + mobile plan that's required to connect the car to the internet) and pretty much negligible when compared to amount of money you'll be spending on that vehicle anyway.
then there are privacy concerns tho. do you trust kia with knowledge of your exact car location, 24/7? (I'd assume it doesn't connect to their servers without the subscription?)
also that information (Exact location of all kia vehicles, with exact model numbers and registration information) seems like a goldmine for car thieves if leaked (or accessed by a third party.)
also, fuck heated seat other hardware/local software subscriptions

you're paying for a backend service and a constant internet connection for your car here though, not for some client side feature that can be easily unlocked

In the end we are in cat & mouse situation
Vulnerability found > hacker cracked it > car company figure it out > vulnerability get patched
It's same issues with John Deere tractor, from what i heard many farmer hire bunch of hacker to crack the software

Curious, what was the "secret Elon Mode" about?

Congratuations, you've fallen for the propaganda. That sentiment is nothing more than corporate astroturfing against effective regulation.