This is a pretty extreme prediction of the consequences of Brexit.
That's the "zero preparation" scenario. If there is no deal, no deal at all, then the existing flight approval regime ends and carriers are not allowed to fly from the UK to the EU .. or the US. https://ec.europa.eu/transport/sites/transport/files/legisla...
Similarly if the customs arrangement is not sorted out, everyone travelling in both directions through Dover-Calais will have to clear customs. At the moment that will involve "operation Stack" all the way down the M20. Similar regulatory requirements problems will arise; direct delivery will almost certainly still be allowed, but "cabotage" rules apply limiting multi-leg trips.
We had two feet of snow earlier this year which resulted in Scottish supermarkets running out of fresh food for a few days. Snow melts. Brexit doesn't.
We had a civil war for forty years in Northern Ireland. The peace treaty stipulated that there must not be a border on the island of Ireland. The government is refusing to present a viable proposal for Brexit that does not require a border.
Unfortunately, “no deal” is looking increasingly likely. While UK rhetoric appears to still be “[The EU] needs us more than we need them”, the EU’s responses have consistently been otherwise.
This may be related to the observation that the UK’s goals and red-lines (when taken together rather than separately) are incompatible with WTO rules.
The "accelerationist" approach motivated Dominic Cummings, as well. It's surprising in that with the names filed off you could present it as orthodox Marxism. The key question is "does the Conservative party (and media) collapse before we get into the situation where flights are grounded and we're running out of food, or afterwards". History suggests that we'll have to end up in a full Winter of Discontent situation before they back down.