It's not just that. How many bugs or ridiculous misfeatures do existing phones have because the OEMs are teaching to the test for benchmarks or just don't care to fix them?

You were reading something on your phone, switched to a different app for 3 seconds and then back, and now it's an error page because you're in a poor cell coverage area but the device is nefariously aggressive at unloading apps to try to eek out a marginal advantage on battery life reviews. Worse, for well-behaved apps that actually degrades battery life because having to reload the app requires the device to do more work than letting it stay idle in the background.

Separate the software from the hardware and you don't have to worry about that, because they can mess up the stock image however they want for the reviews and you just have someone replace it with a version with those bugs removed.