Anecdotaly I've found this to be true. The cause is probably multifaceted. Some things I noticed:

- npm is legit slower in these countries

- Flutter's easy and stable toolchain and great cross-platform support counts a lot more in countries with less specialization

- lower on-disk footprint because no node_modules black hole, actually matters in countries without infinity disk size

- smaller app bundles mean less mobile data

Just some anecdotal observations, there are probably other factors too like inertia