You all may very well be 100% right, having worked in plastics manufacturing for some years. If it's for home use, then by all means store your honey in Lowes buckets or whatever suits you. If a person is wants to sell honey to consumers, however, then the beekeeper has a responsibility to the consumer to ~know~ the honey is safe.
Just because buckets from Lowes are white and look clean doesn't make them food grade -- only chemical tests can verify that. Even if the virgin resin for the Lowes bucket run is the same as the resin for the frosting bucket run, the Lowes run might also have in-house recycled resin, plasticizers, fillers, or traces of dye from a previous production run that are not allowed for food grade products.
On a related note, I have read on Beesource that some beekeepers will not fill jars their customers bring, again to avoid the liability issue of not knowing what might have been stored in that jar in the past.