It's not potential: that's the reporting granulariy provided by the App Store. So you got orders of magnitude fewer users infected on Google Play devices (both your links are for non Google Play Chinese phones). Those half billion infected users were infected for a long time before Apple was finally notified and removed the apps from the store (but not from users' phones) in 48 hours.
That article got that number from what the App Store reports, just as I said. This is the exact same way you would get estimates of affected users on Google Play devices, which is so much less that you haven't even found one article for Google Play infected users. (My guess is that you have found them but didn't bother to post because of the multiple orders of magnitude difference.)
Let's do the worst case analysis of my claim. Let's pretend that the users of all the iOS malware are a strict subset of iOS WeChat users. Let's pretend also that the users affected by each Google Play malware are disjoint. Compare the cardinalities of the resulting sets, and I'll still have orders of magnitude to spare.
