Can a Magento 2 extension use the JavaScript «let» and «const» keywords?

Magento 2.0 and 2.1 support Android 4 browser:

Androd 4 browser:

So, if a Magento 2 extension wants to be compliant with the Magento 2 system requirements (support Android 4 browser), then it should not use the JavaScript «let» and «const» keywords.

Android 4 browser has 8.49% market share on mobile/tabled this (2016) year: