A ten minute wait for steps is an incredibly poor customer experience and, I would imagine, against any contractual SLA. It's not a minor issue, it's Ground Handling 1-01. Now I get that the airlines have them by the balls, but let's not minimise what is a basic lapse of what they're paid to do.
Btw it's not restricted to third party handling as BA would be the case in point in the T4 days at LHR.