This wasn't how the situation would play out in the past.
Castor's blood was still full of the highest-quality neuroblockers that the fleet had access to. Their density decreased over the past few days, but he was still barred from accessing the details of his memories that led up to the events that took place on the auditor's ship.
Castor could recall why he went there. He remembered what was talked about out there and how it all came to Alice coming to his tiny ship and offering her insane talents to support him.
He could understand all of that. Yet, when it came to a specific part of his memories, the neuroblockers buzzing in his blood showed their full potential.
The selectiveness of cutting his memory proved the insane quality of the blockers. Cheaper alternatives would be hardly any different than having his head struck by a hammer in the oldest method of stealing one's memories.