From nc post above, this doesn't seem to be the case, as in PlayStore will auto update the app unless you turn the feature off (so where you download your APK from doesn't matter). Am I misunderstanding something here? Makes me wonder which apps have the different binaries and why they're doing that though.
The Electrum phone setting on the left image below from a device. The Electrum is downloaded from the Play Store. At the lowest part, is the app details which is not in gray because you can click on it and it will take you to the Play Store for updates. The Electrum was downloaded on the Play Store.
The Electrum phone setting from the right from another device. The Electrum is downloaded from a browser. The app details is in gray and not clickable. Which means it will not take you to Play Store which indicated that it is not downloaed from Play Store. But you can go to Play Store to update it, which you should not if you do not want what happened to BitMaxz to happen to you.

The mistake I think BitMaxz did is that he later go to Play Store to do the updates and the automatic update started. The gray out wallet details will also not be gray anymore as he did that and it will become clickable.
For the Electrum downloaded from Play Store, another way around if he wants only Electrum not to auto update and he can do it to other apps. He should do this:
On the Play Store, he should click on the Electrum menu (the three dot at the upper right corner of Electrum) and disable the update as you can see in the image below. It will not affect other apps update.
