if (
  dimensions.width &&
  dimensions.height &&
  dimensions.length // violation reported by unicorn/explicit-length-check
) { }

In this example, packagingData.dimensions is an object, and length could be a string.

As a heuristic to avoid false positives with detecting length or size on variables that are not actually arrays, could we ignore variables that have non-array properties? For example, an array does not have a width property, so if we see that used, we would assume dimensions is not an array, and ignore it.