Final answer:
The reasoning is fallacious as it oversimplifies the potential reasons for not receiving a promotion by attributing it solely to social anxiety without considering other influential factors.
Step-by-step explanation:
The reasoning in the excerpt is fallacious because it oversimplifies the reasons why someone might not get a promotion. The conclusion that the uncle did not receive a promotion solely because of his social anxiety neglects to consider a range of other possible factors that can influence promotion decisions such as performance metrics, company politics, other candidates' qualifications, and more. Furthermore, attributing the lack of promotion to social anxiety alone without evidence to support this claim can lead to a biased and incomplete understanding of the situation.