Google is gathering all kinds of data throughout their apps, so I guess just getting rid of Gboard is just one step of preventing this. Personally I don’t have any real issues with Gboard and it has actually become my favourite across my Android devices since years. There are also a bunch of other 3rd party keyboard apps available for Android.
Considering Nothing’s rather limited ressources, I’d also rather dee them focusing on other software related things, I simply don’t see the keyboard as a top priority.