I checked the guitar where I'd let the oil sit. Long story short, I just spent an hour removing gunk from the side of the frets with Gorgomyte.
OTOH, I took a look at a guitar where I'd just it on last fall, let it sit for a few minutes and "worked dirt and grime free" as per the instructions. Upon close inspection, same thing. Unless Gibson glue is green.
On yet another hand - my 2017 Tribute came with a pretty dry-looking fretboard, which didn't change with the annual oilings. Now, it's significantly darker - it looks healthy for the first time.
Regool is right, as is Kidblast. Letting it sit for five seconds won't hydrate a piece of wood. OTOH, letting it sit for 30 mins may eventually fook up frets.
So letting it sit for 30 mins should only be done if the wood actually looks thirsty and downright miserable. If it's been through ten Swedish winters or so, in my case.