Like you say, it is moderately de-googled, which is a fantastic improvement over stock android any way you spin it. I believe that was the point of the original commenter, as it is mine. However there are those blobs that do get left in (in every ROM, including even DivestOS which is the most aggresive in this regard). Install a firewall or network monitor on a device that's only been somewhat deblobbed and you'll find that they are not little black boxes sending all your data to Google, but instead are there to do things locally like software interaction with hardware in the phone that is from another company like Broadcom.

Any ROM on a Samsung phone probably lags on security updates due to Samsung itself being slow to release them, though they do seem to be doing better lately. If the ROM itself is slow to push updates, the most you'll wait is 2-3 months. That's pretty much not a problem unless you're being threatened by state level actors, and is the state that the majority of stock android users are in. In fact, stock android can often be years out of date because their manufacturer just doesn't put them out.

Regarding dependence on Google services (play store of otherwise), let's be honest, GrapheneOS users almost always install sandboxed play services, work profile or not. I don't blame them, it's how I have Graphene installed on my phone. However, this not a privacy oriented thing to do, it releases a flood of information to Google, much more that a simple connectivity check or SUPL ping. It's not as much as fully integrated play services though, which is good. MicroG may be theoretically less secure, but it is certainly more private. It simply asks for less information from you than play services do.

The relockable bootloader subject is bit of a pet peeve of mine. Personally, I do choose to use a pixel so that I can have that added security, as it does have value. However, to say that without a lockable bootloader you are compromising your security and by extension privacy is what i would consider an overstatement that creates fear and uncertainty. Your security and privacy only become compromised if a thief steals your physical device then also has the know how to execute a sophisticated software based attack on the phone using adb. This just isn't something that happens. In the many years I've been around the android ROM community, privacy/security focused or otherwise, I've not heard of this happening even once. To tie it back in to the OP, this scenario is actually a perfect use case for the app mentioned in this post, it offers you the ability to remotely wipe the device if it's been stolen.

It can be an issue from a software angle though too, but then you would have to download and install a piece of malicious software that is specifically targeting phones without verified boot. At that point there is a greater issue though, because you can download and install malicious software that is targeting phones that DO have verified boot active just as easily. All that's necessary is to be well informed and have good security habits and behaviors, it's how desktop competant windows and Linux users have gotten along just fine all these decades.

It's easy to get swept up in the security dogma of the android ROM community. In my opinion, some of it is helpful, but some is not practical or useful for every day users.