Turning on hotspot automatically turns off my Wi-fi in my Moto g4 plus
The device has to support 2 WiFi frequencies, and the OS has to implement the feature (e.g. Huawei D2 and Samsung S7/Edge), or else you will only get either WiFi in or WiFi out. I've never seen any mention of the original G supporting the feature either, and since I've owned an original G myself, I can say that it can't do it in my experience.

The only way that was able to do it on non-OS-level was FQRouter2, but it's now obsolete and might not work.