I think 12 minutes was on the range of charge time difference between 25w and 45w charging on the Note 10 Ultra from what I recall so this appears to be about right.
I bought a 45 watt charger when I had the N10 Ultra. The biggest plus was really just that it can charge my Elecjet Portable battery at 45 watts. Though, it's my gf that uses the battery most often to charge her iphone. I rarely run out of battery and I got the Samsung wireless portable battery with my Note 20 Ultra, so I don't use the Elecjet battery often. It's possible I could use it for other devices as well, so having a 45 watt charger isn't necessarily a bad thing as more and more devices are going to be using USB-C. In fact, I picked a Square Terminal for my business last night and saw the included charger was 45 watts. Rather than plug it into the included charger, I used the Samsung 45 watt charger and it charged up fairly quickly. I've also used my Elecjet battery to power my work laptop. I can conceive just taking the Samsung charger with me and be able to charge up my phone or my work laptop without having to pack so many chargers. If anything, it would offer flexibility...