One plus launches one plus 9 series in india and it supported only few bands despite of a flagship phone
One plus 9r - only one band N78
One plus 9 - two band N41 and N78
One plus 9 pro - two band same as one plus 9 N41 & N78
Why limited band in india
You see the most common band supported in india is N78 because it's improve version of 4g in india it's minimum frequency is 3.3 ghz and maximum is 24 ghz which will come in future and second thing is cost cutting I think
Hardware limitations
In past in us one plus has upgrade bands via ota update in United States but I think one plus has not pay royalty for hardware update to Qualcomm Snapdragon
Fully future proof 5g smartphone