As that article rightly says:
Keefe said the phytosanitary checks legally required on both sides of the border were a bigger challenge than the high-profile issue of customs checks that is currently dividing the cabinet.

“If we are all happy eating frozen meat then it’s an easy win, but if we want fresh food and having it on our shelves 365 days a year then it’s a big problem,” he said. “We export about £8bn of fresh produce a year and import £12-13bn. That amount of fresh produce going backwards and forwards is far more of a risk for the government than is anything of customs or duty.”

As pointed out before, this will be more of a problem to the EU sellers than to UK sellers, so it is in the EU's interest to come to an arrangement over this.