The phone manufacturers don't have much of a choice unless they are willing to ditch support for all the proprietary Google parts of Android. People probably won't buy android phones without play store access.
I just bought an android, there was no default search on it and playstore works. As I booted it up it asked me what search engine I wanted, Google wasn't on top or preselected.
So yes, phone manufacturers have a choice here, they don't have to make Google the default.
It's likely not about the brand, but about the location. As a result of the Android anti-trust lawsuit in EU, Google has shown a search engine choice screen at initial setup since (I think) 2018. They also unbundled Chrome and Search from the other proprietary apps.