I’ll echo what Gembo has said, i’ve had numerous rigid crane vehicles for the test over the last 10 years (up until around 2015), with cranes ranging from 1999 to around 2010 (various makes, mainly palfinger) and none from memory have been fitted with any sort of visible pin or catch type locking device at all on the legs (mainly been cranes around the 19-25t/m mark with only two front legs).
Would need to have a look at the testers manual is it a case of inspect and check operation if fitted?
Never had an issue with any test failing regarding crane leg locks, never even been mentioned. One roadside inspection I can remember and nothing said either.
Sounds like this is more testers discretion in some traffic areas?