In the now distant past, all manufacturers of electronic components published very extensive datasheets, application notes and user handbooks for all the devices that they were selling.
One could typically learn much more electronics from the application notes or maintenance manuals of the vendors than from university courses.
This included LEDs. For instance Hewlett-Packard published a good handbook for their LEDs, where many useful techniques for designing with LEDs were explained, including what you mention, that LEDs may have higher luminous efficiency at very high currents, so for achieving a given luminous flux you may save energy by operating them with pulsed currents.
The use of multiplexing in the interfaces of multi-digit/multi-character LED displays (e.g for clocks or calculators) not only reduces the number of wires in the interface, but it also improves the energy efficiency, because only one digit/character is powered on, at a much higher current, but for a much shorter duration in comparison with a non-multiplexed display.
During the golden era of electronics documentation, it could be difficult to get the vendor documentation, even if it was usually free, when you were located far away, e.g. in another country.
When the Internet has appeared, for a short time it solved this problem so you could be located at the other end of the world and still access easily the datasheets, application notes and user manuals.
Unfortunately, very soon after that, towards the end of the nineties and much more since 2000, the quality of technical documentation has degraded tremendously, so you now have easy access, but to much less useful information.