The Sin, however, is in claiming that using this client allows one to use Bitcoin in a trustless manner. If one does not validate all transactions from t=0, then one is outsourcing the chain of custody to others. Others that you must trust.
It works this way for many years already, Core and BU not validating old signatures. You can hardly use Bitcoin in trustless manner, every one must trust something, be it node software, operating system or the hardware it runs on - you cant make or check in full everything.
are.