Know of someone who was in a heavy jet and had a hold slapped on them very quickly them in the cruise. As they turned downwind and still getting their act together they almost stalled the thing; had the shaker going off and lost a few thousand feet in the recovery. Thankfully noone was below. Obviously it is an extreme example high winds and high(ish) altitude but possible none the less.

It still has nothing to do with turning downwind.

Exactly that.

Modern turbofan powered transports have too high Mach No where mach effects have significant effect on stability and controllability (it is way above Macrit or Mmo) and too low power output at altitude to reach altitude where 1g stall and Mach buffet intersect. Valid when HTBJ was written. With higher bypass and improved aerodynamics, even more valid today. If you fly Airbus: altitude where Vls and Mmo meet is way below hypothetical coffin corner, which doesn't imply that it should be taken lightly.

Mach buffet is anything but stall. Depending on design one may experience pitch-down, pitch oscillation, trim reversal, roll reversal or many other unpleasant surprises but there's no rapid onset of drag and loss of lift that goes with pushing the aeroplane over AoAcrit.

When frames of reference are mentioned, here's another myth:

FBW Airbus in manual flight maintains 1G with stick neutral in pitch, therefore at higher FL, where gravity is weaker due to distance from the earth, it will pitch up to maintain 1G so constant nose down pressure is required to maintain level flight.

I am pretty certain that ensuing furious FCOM quotes and stories of "I've seen it" or "My friend has seen it!" will help me to somewhat explain origin and persistence of aviation myths.

I obviously wasn't there so I'm not saying it happened like this but it is worth thinking about..... Many many airline pilots think that the top of the lower amber band that provides them 40 degrees bank to stick shaker, implies that as long as they are above that speed, then they can safely bank 25 or 30 degrees into a hold, at altitude, and expect the aircraft to maintain it's height and airspeed and fly around the hold no problem. There is no such guarantee. I personally think that, or a windshear, or both, are the most likely culprits for your scenario.

"where gravity is weaker due to distance from the earth"

I'd be very impressed with the sensitivity of the accelerometers which would notice the half a percent(ish) difference at 40000ft

Its a four star hotel
The crew bus will be here in 5 minutes
The load controller has checked the holds
The FO will back you up
Creosote Keith is really a nice guy
Bishop is joining Lufthansa
BA want BMI pilots

It's just a temporary paycut, while fuel prices are so high
You'll be doing your upgrade within a year or two at most
There's no money in freight
Age 65 retirement will decrease time to command
Captain we've finished, we're closing the holds
We put safety first

Security checks are contributing to the improvement of aviation safety.

Captain we're ready, the last passengers are just boarding now
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A girl in every port
Ryanair, the high pay airline
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Any manufacturer promised new airliner delivery date
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The tug is on its way

Chocks in position
There's a passenger missing, but with no checked baggage
The stairs are on the way
Our people are our most important asset
Are you refusing a duty?

Spanish 'Calm' regarding the wind and they don't want to change the rwy.

"we are a safety first conscious airline and nothing comes before that."

"the door to flight ops management is always open, and so are our ears."

'we operate a no-blame culture."