Rafe de Crespigny does write this passage after talking about "hostile sources", which he mentioned the Cao Man Zhuan before this example, citing several unflattering stories. He then mentions the story from Sun Sheng. Both of these are in the same paragraph with no distinction between the two.
He used Cao Man Zhuan as a direct example. Saying
Cao Man zhuan, for example
. However, he did not used the Yitong Zayu as an example. Just because the Yitong Zayu appeared immediately after doesnt mean it was a reference to the hostile sources thing.
Also, if u looked at the reference, he wrote 53 - the Cao Man Zhuan portion - using only 2 sentences to provide background information.
Meanwhile, the Yitong Zayu had two big paragraphs filled with elaboration on the historian life, his work and the connection with various sources.
One can wonder why RDC would go out of his way to elaborate the Zhang Rang tale and then proceed to offer his opinion on it with the " but we may assume that his family connections also served to protect him" if he had any doubts about it.
This is also in contrast to RDC treatment of the Shishuo Xinyu in the following paragraph where his elaboration of the account was not one of acceptance but an explanation of its lack of reliability.
Also FWIW, he has yet to criticise Sun Sheng work AFAIK. In fact the only thing that can be read as criticism is him pointing out Sun Sheng 'jaundiced eye' in the reference which isnt a criticism of the reliability of his work but more of Sun Sheng's cynical view of the 3K period individuals and events.
This is something which Pei SongZhi criticised Sun Sheng for also when it came to the Jiang Wei appraisal IIRC.
Finally, in page 22, RDC uses Sun Sheng Yitong Zayu as a direct reference.
Cao Cao’s scholarly interests are mentioned at this point in his biography in Sanguo zhi, and his work on Jieyao and Sunzi probably began about this time, but it is not known when they were completed. It is likely that a great part was written during his period of enforced
retirement in the late 170s, on which see below, and perhaps during the 180s. Thereafter he was intensely engaged in practical aspects of warfare, and probably had less time for theory.59
59 Cao Cao’s interest in books on military matters is mentioned by Sun Sheng’s Yitong zayu at SGZ 1:3 PC. For a more detailed discussion of his work in this field, see the section on Cao Cao and the Art of War in Chapter Seven.
In contrast RDC throughout the entirety of Imperial Warlord repeatedly label 'Cao Man Zhuan' as hostile and propaganda, albeit using it as a reference when it came to the discussion of Cao Xiahou connection.
In fact, one of his last chapters - which RDC uses to explain the fictional background of Cao Cao ' contains many outright criticisms and dismissals of Cao Man Zhuan.
Theres the distinction.
Liu Bei did nothing wrong.