What are the (potentially toxic) implications of this myth? First, that the founder/CEO isn't a "true founder" unless he or she is entirely self-sufficient. Second, that hiring an office manager or personal admin early on signals weakness -- that it's the founder being precious or high maintenance. Unheroic.
You'd be surprised at how pervasive the myth is, and how many founders are either too self-conscious or too caught up in the scramble to even consider the benefits of hiring for this role. A solid office manager/admin is a really strong hire, and if anything, hiring one should signal maturity. It shows that the CEO knows how to segment the tasks into those he/she should be focused on, and those he/she should be delegating. It shows that the CEO knows how to value his/her time and energy appropriately.
This may seem obvious to many, but certainly not to all.