Certainly, the WhatsApp userbase is skewed. But most of WhatsApp Android users are also Google Play Android users (certainly not all, WhatsApp publishes the apk directly), so if WhatsApp doesn't want to cut off X million users on Android 5, but Google is ok with not supporting it, Google almost certainly has a higher threshold value required to keep support. I'd guess the Android 5 users with Google Play and not WhatsApp outnumbers the Android 5 users with WhatsApp and not Google Play, but none of those statistics are public.
With the number of Android devices out there, it really makes more sense to think about it in actual user/device count rather than percentages.
With the number of Android devices out there, it really makes more sense to think about it in actual user/device count rather than percentages.