Interesting! I wonder how much of the indistinguishabilty is just them catering to their audience looking for North Indian recipes. There are definitely a lot of Nepali recipes that are very far from Indian cuisine.
It's almost all catering to local taste and what's expected. Nepali food is good but it's not as rich as what you'd get in a restaurant. Daal baht (rice with a thin lentil soup) is not what people expect if they pay $10-20. Hell, most northern indian restaurants feature foods that are way richer than you'd see in real home cooked cuisine. The restaurant versions invariably have way more heavy cream and butter than would ever be used in a typical home.
North Indian cuisine is more established globally because North Indians were either forced to seek economic opportunity abroad. It wasn’t then alone, but the numbers in many areas of the world make it clear off the early waves to the Middle East, Africa, England, canada, the us, and beyond.
Partition uprooted and scattered many families from the generally 1900’s Indian subcontinent across the world in waves.