We also had no problems with PropellerAds, but Adsterra was more suitable for us.
Let me summarize: there are local rules that companies have to follow.
KYC - Know Your Customer ?
AML - Anti Money Laundering
Are legal policies in financial services that require professionals to make an effort to verify the identity, suitability, and risks associated with maintaining a business relationship. The procedures fit within the broader framework of a bank's Anti-Money Laundering (AML) policy.
Since PropellerAds is the company (legal entity) that sends (respectively the bank) you (natural individual) money, it has to make sure that all the guidelines are followed, otherwise PropellerAds will be fully liable in case of fraud (which then quickly runs into the millions in the admarket). Since PropellerAds consists of different (sub)companies, it depends on where you live, to which company you will be assigned and which KYC/AML requirements are necessary. That's why some companies (PropellerAds) have different requirements than others (Adsterra).
Yes, the business world has become complicated in recent years...