This same question of cutting the plug off came up at an IAEI Conference last year.
The issue was cutting the plug off a pump instead of installing the hard-wired version (which cost a bit more).
The Code Panel rep from UL went ballistic over that philosophy; when he calmed down he explained that even though the units looked absolutely identical from the outside, there were construction differences on the interior of the pump/motor. In the case of that particular pump/motor assembly, the materials of some of the internal seals keeping the motor dry were even different.
In addition, the tests used to UL List the plug-in and hard-wired units were different.
The real issue was that cutting off the plug and hardwiring was in violation of the UL Listing and Manufacturer's instructions.
That still finds its way back to being a violation of 110.3B, since it is being installed at variance with its Listing requirements and limitations.
