indeed there is only a few countrys that need a high altitude chopper india being one of them that would include china and pakistan bu not only for high altitude but for coutries that are very hot and humid which expands to many other countries
Of which we have both. That is why the trials include both desert and high altitude phase.
Like members have posted here, we have been flying IAF Cheetals (upgraded with Shakti engines) at levels exceeding 23000 ft with posts at 21560 feet being serviced by them without a major degradation in capabilities.