When ATC asks a pilot to fly a holding pattern, he expects the airplane to stay at the required altitude in the sector of the holding pattern.
For the vertical direction, the question is straightforward: how much can the aircraft deviate from its assigned altitude?
For the horizontal direction, the question is more tricky: can the pilot fly a larger than standard holding pattern (lower turn rate, straight legs twice as long as expected)? What happens if on the contrary the pilot flies the pattern in less than 2 minutes?
Bonus question: what prevents the pilot flying an 8-shape instead of an oval one if he stays inside the holding pattern area?
EDIT: my question is really about the limits. It is obvious that a deviation of few millimeter or less than 10 seconds is OK, but at what point does it start to be not allowed (in other word, what is the precision required)?
To better understand the problem I want to address, my comprehension is that as long as you stay in the assigned sector, separation is ensured without any ATC intervention. Thus, I see no added value to be as precise as possible as long as you stay in the assigned sector. You may circle closer to the holding point, the separation will still be assured. But what happens if you fly farther away but still in the assigned sector? And what happens if you fly a non standard shape but still inside the assigned the assigned sector?