To me it seems like a way to really consider internet to be a public utility such as water and electricity. I'm sure there is a law that says any new construction requires it to be connected to the electricity grid, even though it would be pretty unreasonable to not connect it to the grid. Does that mean there is no need for it to be a law?
At least this way you can have a good expectation of a new buildings utilities.
When you set a minimum standard, something that could have been bought for less that didn't meet that standard will no longer be an alternative. So some people will have something better and others will not have an option that they once did.
It can make a maximum difference in cost of about 1% of the final sale price, probably less given the cap and average prices of new build properties. I don't think it'll have a big impact on whether the houses sell, we have a huge undersupply of new housing.
At least this way you can have a good expectation of a new buildings utilities.