I would suggest, from experience, that the workload on the base leg is moderate in ensuring the jet is on the correct vertical profile and the landing checklist completed by 1000’ AAL, (as required by most operators now.)
Normally, as Flaps 40 are rolled out, and speed is being reduced to the final approach speed, landing checklist being completed, it’s time to turn base and commence descent. Therefore there’s rarely any sustained S&L flight at the end of The Downwind Leg with high thrust levels.
In the interest of stability, and avoiding unwanted ‘flagging of parameter exceedences’ (and overloading the PM at a rather condensed period of monitoring / assisting) , It’s quite prudent to be fully configured prior to turning onto the base leg (45 seconds After the abeam ldg threshold point in nil wind) “these days”.
(Also note the 1-1.5nm final, ie 300-450’ AAL - our company policy is wings level on final no later than 500’ AAL.) - like it or not, everything has been dumbed down / fat added since that diagram was published.