I was talking to a customer last week who bought a set of the girder forks. They looked fine, a very good copy, but materials and machining accuracy wise were terrible meaning new spindles had to be made to get them assembled on the bike. Who knows what material spec they are made from.
I was in India 2 weeks ago visiting suppliers, they have truly world class facilities out there, and next door schoolkids bashing parts out of old cars into “new” motorcycle parts. You just need to know where and who you are buying from and what the raw materials are. Unfortunately you cannot usually tell material quality just by looking at a part, pistons included.