Some smartphone manufacturers implement particularly strict energy-saving regulations in their software. This causes apps to be terminated unexpectedly and, in the case of the realme XT, even the GPS functionality suffers, which means that the otherwise good smartphone is worse off than it should be.
https://www.notebookcheck.net/realme-XT-Energy-saving-isn-t-everything.450454.0.html
So every power saving function can be easily disabled? More details.
It's already common that most Chinese smartphones come with "aggresive" power saving as default behaviour. That includes Xiaomi, Oppo, Huawei, and even OnePlus. And then it's got worse, spread to Samsung, etc.
Source: xda and dontkillmyapp.com