Do you think there was better ROI to that time spent than now with the smartphone? Like, you "killed" those 5mins by learning something (however esoteric it may have been) versus sucked into a nonsensical Tik Tok vortex?
I took this to mean the niche is "learning something interesting in a short amount of time" not "killing a short amount of time" so to me the OP implied they were using the smartphone to learn and not browse TikTok.
This behaviour is normal today, but 40 years ago people other than me had the ability to wait patiently.