Most builders are building on limited budget.
During the building in case of mistake they can make another part.
Limited budget not allowing them to have proper helicopter flying lessons before testing of own helicopter.
One small mistake in piloting and they can make another helicopter again.
BTW not bad to follow and learn on other people efforts and mistakes...
https://www.youtube.com/channel/UCAC...9Cn5FA3RbXHt-A