Size of doorways, weight bearing capacity of floors, electrical service parameters, environmental conditions, etc.
e.g. Does it actually handle electrical voltage fluctuations of +/- 1V, or whatever is advertised?
The guaranteed parameters of a fully set up machine:
Minimum performance metrics, software compatibility with whatever the sales department promised, maximum power draw, etc.
e.g. Can it reliably hit X metric (FLOPS, IOPS, Integer calculations, etc.)?
And so on.
Or does the customer need to take on some risk and hazard associated with installation, configuration, initial boot up, etc.?
e.g. If someone buys with the intention of using it up to X FLOPS, and the machine only delivers Y FLOPS once it's all said and done, what happens?
Otherwise I would imagine it would be a major selling point and be advertised publicly.
But if it is a complicated enough internal issue for that not to be the case, then my apologies for pestering.