Why not? That can be construed as abusing their 'monopoly' over shelf space and foot traffic, it's unfair competition that displaces other legitimate businesses.

Incidentally, in the Netherlands a lot of supermarkets stock a 'shared house brand' called Gwoon. Usually the cheapest option by far and decent quality. I don't know what they do to keep prices as low as actual house brands, but it seems possible.

I’ve been thinking about it and if there had to be a common rule for all these cases, I would say “yes”.

However, if it was possible, I would set a threshold maybe based on an annual revenue. Let’s say I run a small board game store, where I sell games from other producers, but also my own games that I published. I’m a small entrepreneur, should I be prohibited from exposing my products more?

Amazon, Spotify and some supermarket chains have such a dominant position in some markets they can abuse their position, they should be under scrutiny, but not small retail companies that want to try to create something on their own