Yes, it is designed that way. The older three screws had a shorter pin, just like a Colt. And just like a Colt, when firing heavy recoiling loads, if the latch is not secured, it is possible for the pin to work its way out and get lost. When Ruger redesigned the New Model in the 1970s they included the longer pin, that would not easily get lost.
You can replace it with a shorter Belt Mountain pin if you want.