Your LFS are on hallucinogenic drugs.
Sorry, you asked for my opinion.
Plants are neither here nor there with cycling. They will use up some nitrates in the water, but that doesn't affect cycling itself - the purpose of which is to build up bacteria to convert ammonia and nitrite.
If you're doing fishless cycling, I recommend you do it without plants. If you're cycling with fish, plants will just give your fish some places to hide (ie: security).