I can't read the link but we've the same thing in Ireland. I've always assumed it stemed from shops being family owned. e.g. We have a stationary store that was originally called Eason and Sons which when said quickly sounds like Easons.

There'a s few other examples but that's the one that always stood out to me

It's British too. Tesco is always called Tesco's.

British supermarket Sainsbury's even put it in their logo.

The actual name of the company is J Sainsbury plc.

Sainsbury's is a reduction of John Sainsbury's supermarket, so they need sense. Just like Wilko's is Wilkinson's general store.

Well obviously but poster's point was that it's a British/Commonwealth colloquialism to do that.

It started as "J Sainsbury" with no apostrophe s. Then it changed it registered as "J. Sainsbury Limited" in 1922, again no 's.

"John Sainsbury's supermarket" was only contracted and picked up much later for marketing.

Or even Sainsbo's ;)