It's not a good idea to make blanket statements like that. Different projects have different circumstances. It is not always possible to focus on as many platforms as possible for various reasons. Having said that though, if a publisher decides to commit to a platform early on in development, it's certainly just a matter of good management to budget out the resources and time needed for the port.
It's not really a blanket statement though. I can get that you cant focus on many platforms because of budget constraints. I can get that for smaller projects that run on non multiplatform engines or which have a too small scope.
But on the other hand, countless smaller publishers manages day and date multiplatform releases just fine.
I'm talking here about one of the biggest publisher worldwide. If you cant make inhouse port because of various reasons, you can always contract help.
Then again, countless publishers, even indies can manage it. And Nier is just another exemple of how it's a better investment than releasing later. And then again, we also have concrete exemples thanks to SteamDB leaks of SE delaying port releases that were ready 9 months before release.