[docs] How to avoid fetching different assets during fluctuations

Consider this scenario:

My phone is connected to WiFi(4g), the power goes off, and my mobile data(2g) kicks into action. If there were multiple assets fetched for 4g, all their low quality equivalents will now be fetched.
This will also happen when I am travelling between places as my data speed keeps fluctuating.

I am not sure what the solution to this problem is but I believe we shouldn't be replacing assets that are already fully loaded.