According to Disney themselves, it’s 38 minutes via monorails from Epcot to MK. Adding in walking especially if you’re coming from the back of EP, potentially waiting for a monorail, tapping in at MK, you could easily add 20 minutes. I absolutely would side with “at least an hour”. Especially if you need to get somewhere on time.
According to Disney, it’s 40 minutes to MK from the BC. Throw in a 10 min walk to the BC, and you’re also pretty darn close to an hour.
So again, if you are trying to get somewhere, especially something that you paid to be at, I absolutely would want “at least an hour” to get there.