For those unaware, this phrase: "The lump of cognition fallacy" is a derivative of the classic economic fallacy: Lump of Labor Fallacy (or Lump of Jobs)

Google AI describes it as:

    This is the most common form, often used in debates about technology, immigration, or retirement. 
    Definition: The belief that there is a set, finite amount of work to be done in an economy.
    The Fallacy: Assuming that if one person works more, or if a machine does a job, there is less work left for others.
    Reality: An increase in labor or technology (like AI or automation) can increase productivity, lower costs, and boost economic activity, which actually creates more demand for labor.
    Examples:
    "If immigrants come to this country, they will take all our jobs" (ignoring that immigrants also consume goods and create demand for more jobs).
    "AI will destroy all employment" (ignoring that technology typically shifts the nature of work rather than eliminating it).