Samsung isn't flexing because they are like all other companies including Apple, Google and Microsoft, if the cash is flowing, no reason not to remain content and play it safe.
I'm personally against Seamless. It complicates the partition structure and allows for equal parts fallback security as it does risk. Lower end devices definitely would benefit but flagships take what, 2 minutes to install and reboot? I don't Like the idea of update files sitting on a partition i cant access if something goes wrong. Pixels at least have unlockable bootloaders so youre rarely completely hosed.
Samsung you have ODIN but that's far from beginner friendly AND seamless would presumably kill ODIN.
Yes... Tizen, long ago, apparently not long enough to be forgotten by some

. Tizen on TVs was a nightmare. However, it is to be said that outside of no apps, Tizen was IMO better than WearOS or whatever the hell Google has renamed it to for the 5th time. My GearS3 watch battery lasted, the experience was smooth (again just not many apps) though I rarely use apps with my "Google-fied) Samsung watches which have microstutter and comparatively bad battery life.
So Tizen was what Stadia (among countless others) to Google. A half-assed, low effort attempt to push something new without the commitment or drive to make it appealing.