I don't use the 71b, but I do use a form (of my own design) for most of the apartment appraisals I perform, up to maybe 30 units. It's a variation of the commercial report format I use, which itself is an updated evolution from the UCISAR that TAF developed back in the 1990s. Nobody will be finding any omissions or obsolete USPAP references in any of my reports because I control the format.
I've been using this suite of appraisal "forms" for most of my clients for 12 years now and I've never gotten any user pushback on it. I have variations that I use for SFRs, land, commercial, and multi-family, and they all share the same layout.
I should mention that the 71b is only 4 pages long, not counting back-n-forth addenda; whereas my multi-family format is 11 pages before the housekeeping and addenda. It reads front-to-back like a narrative so all the content goes into the main body of the report. I can add/delete sections or expand any of these sections as much as I want to - which I sometimes do.
Not counting the mixed use properties I've appraised, I've done 14 of the multi-family assignments this year, which is probably typical for me. I think I've only written maybe half a dozen narratives this year, and most of those were because the assignment type had too many moving parts or otherwise required far more discussion than would fit in a structured format. Most of the mixed use properties I appraise are small properties and I put those on my commercial form.
Different strokes.