I started my B737 life in an operator that actively used A/T in 'speed off' mode on a manual approach. No issues, ever, despite coming from an utter dinosaur of a smaller jet.
I continued with another operator, a few years later, where the same practice was common place. Never any issues there, initially, and we flew plenty of challenging trips, and not a few go arounds which were non-events, using an A/T Armed/speed off setting. Then the training department started to change its culture, and along with protracted wordy briefings came the dictate that 'speed off' was not only no longer to be used, but was expressly forbidden. Why? Because Boeing said it Must Never be used. Oddly, training manuals didn't really reflect this, and after many queries from folks who'd never had any issues with 'speed off', a supporting 'memo' was supplied which quoted an extract from Boeing. The exact words were curious, and the main gist being that while Boeing 'does not recommend...', this had been interpreted as 'Boeing recommends do not...', and thus Boeing 'forbids...'
I moved on through several different types and operators for a few years, including one 737 operator where their go-around SOP had the PF reengaging the A/T, and the PM checking that it had been reengaged-
Here's the mouth music-
PF: 'go-around, flap-15, set go-around thrust' (PF sets A/T switch)
but found myself back on a B737 in Europe after 6 years, with a company that happily encouraged the use of 'speed- off', but also accepted A/T off if preferred. And so life continued for a short period of time until some folks from a Golden-harp operation took over a UK located/EI AOC, and all of a sudden, an edict was passed that clearly stated that A/T MUST be turned off, and that 'speed-off' must NEVER be used, and as further fact supporting this, an extract of a Boeing statement was issued as part of a flying notice. The old familiar words 'Boeing does not recommend...' being interpreted to state 'Boeing recommends do not...' and that the use of 'speed-off' is expressly forbidden (ostensibly, by Boeing). Along with this came an implied threat that anything else would be seen as a deliberate breach of SOP.
I'm now with another operator where this very same 'interpretation' of the by now familiar Boeing memo exists, but with a caveat that it doesn't apply if there is appropriate training in place to cover the use of 'speed-off'
I've seen plenty of notes and ops manual entries, etc, where the recommendation of completely turning off the autothrottle when flying manually is concerned, and I've seen plenty of extracts quoted regarding the 'Boeing does not recommend' or similar. But if Boeing really did forbid its use, why would there be a caveat about the training of its use? Why would the system still allow its selection (..or deselection)?
To me, it strikes me that a rigid, but flawed, interpretation of a memo addressing a 'general' technique has led to an equally rigid and somewhat flawed SOP and a degradation of the operation.
but that's just me.