It's fear, plain and simple. Regardless of all the fireCalc simulations, pensions, SS, etc. some people are so afraid of going to $0 earned income that they perpetually delay. I remember a similar conversation I had one someone on this forum who (if I remember correctly) had annual expenses of under $40k, a mostly-equity portfolio around $1.6M (already a 2.4% WR), a paid-off home he planned to downsize, and substantial cash flow from a pension and (later) SS. Yet he kept talking about one-more-year 'just to be safe'.
slugline may be right - deep down the poster may just not know what to do in ER.
also, while 54 might not seem 'early' to those of us on this blog, it's a good decade earlier than the typical worker in almost every country on earth. So sure, I personally count anything before 59.5 as "early" - but that's just me.