I don't know - people from Huawei just lost their inspiration or just decided to go the easy way but it's not important. The important thing is almost identical design of both G9 Plus and Maimang 5.
System: Android 6.0 (EMUI 4.1);
Screen: 5.5" 1080p;
SoC: Snapdragon 625;
RAM: 3/4GB;
Storage: 32/64GB;
Cameras: 16/8MP;
Battery: 3340mAh;
Others: Fingerprint scanner;
Weight: 160g;
Price: Yuan 2399/?.
2399 Yuans gives around $360, EUR 318 or GBP 275.
Similarities doesn't end with look - even 3GB RAM + 64GB Storage gives exacly same same components used in Maimang 5! At the moment it looks like Maimang 5 Bis and nothing new. Maybe There will be differences we can't see now, I have hope this is the case.
Source: GSMArena