I am quite amazed that this keyboard backlight issue doesn't come up more often among Switch users.
When I buy a product that says: 'Illuminated keyboard', I expect this keyboard to be illuminated whenever and how long ever I want it to be on. Especially when the unit is powered and not on battery. This 5 second timeout is really a nuisance.
Would you tolerate a energy saving bulb, which goes off after some time (in order to save energy) ---- no, I'm sure you wouldn't!