I was thinking the exact same thing. I have a phone, I don't need to have my watch turned on when it's charging. I tested my GW4, and it charges way faster off.
I don't know what to think after reading your article and watching several YouTube videos about this newly released Galaxy Watch5. It appears that Samsung should have done further battery charging tests or perhaps hired someone from OnePlus to help them understand what "true" fast charging means. The Galaxy Watch4 Classic that I wear takes over two hours to fully charge and only marginally charges quickly when connected to a 25W fast charging brick. I have a plethora of 30W, 25W, 65W, PD, and Anker charging ports to use when my Galaxy Watch5 Pro arrives in a few days. As the expression goes, time will tell...
Samsung advertises the Galaxy Watch5 series as featuring a new fast charging feature. Theoretically, the Galaxy Watch5 and Galaxy Watch5 Pro should recharge 0-45% in just 30 minutes. However, an independent test has shown that this is unachievable in practice. Instead, new owners of either smartwatch should expect to wait a lot longer for either smartwatch to reach 45% charge, let alone full charge.