It presented limited flexibility for couples who are in different stages of life. DH is 71 and collecting SS. I'm 62 and don't plan to collect till 70 (subject to real time change in plans.). We have rental income. Our savings/investments are treated as joint from a withdrawal POV, but some are titled individually (IRA/inherited money).
But - if I put in 0 for SS to remove that factor/limitation, then put in our rental income for a pension (which is what I do in firecalc),and my (younger) age... I saw a withdrawal rate similar to what we're currently taking.
Not planning on an annuity - but that (like when to take SS) is subject to change in the future if interest rates make a SPIA make sense.
I also noted if you slide the annuity bar - it does NOT adjust your retirement savings down by the same amount... So a lot of people might misinterpret the results.