The Test & Integration (T&I) stage may be the first time your CubeSat is verified by a third party against the specification. The integrator takes a “hands-off” view of your SC during T&I. Decision is simply Pass/Fail.
Traditionally, 1U CubeSats must conform strictly.
3U CubeSats (10x10x30cm) have more leeway, as they are alone in the P-POD. Some P-POD customizations have been done, e.g. Delfi-C3 w/X-POD.