Tim Cook specifically mentioned the 15% yesterday at the hearing for a certain type of subscription app, which Amazon Prime falls under. Not sure about the Baidu case.
As a former PM at Shopify, I think the risk of this is pretty low. Shopify optimizes for building things into the core product that at least 80% of the merchants can use. On top of that, they are pretty slow to get things to market given they are a big company. That said, the risk is not zero. But if you pick a good niche and stay differentiated, it’s less than you’d think.