Yep, it' "just" about allowing other payment providers to have access the NFC hardware.
It's not about having access to the ApplePay backend infrastructure, they simply wan't to be able to use the NFC chip to read & write custom data.
Allowing NFC access would not add any security flaws to the Apple Pay System, simply because the data needs to be interpreted and is broadcasted on activation by the NFC terminals anyway. The security relies inside the backend infrastructure that handshakes and interprets the encrypted data read and written by the NFC hardware.
By limiting the NFC hardware access Apple makes sure no other Payment provider is able to offer a NFC payment on iOS, making it impossible to compete with Apple Pay, which is anticompetitive.
It's simply wrong to let one or two companies de facto take over the whole payment infrastructure and services of multiple countries.
But yeah Apple loves to twist the NFC topic in a way that makes it sounds like opening the pandora box to Apple Pay frauds. The same they do in other topics.
The bolded / red word you used is where I disagree .
I think that term is thrown around quite a bit (Not calling you out specifically). Since the iPod days, and now iPhone / iPad, it is clear that people are buying into a closed ecosystem. Remember when the iPhone didn't have an App Store, had they continued the fully closed, no 3rd party applications would we still call them anticompetitive? There actually is competition, one can buy an Android, feature phone, or no phone at all, there is zero worldwide requirement to buy an iOS device.
In a similar note, can Sony not offering their in-house Playstation titles to Xbox customers also be considered anticompetitive?
I am not saying Apple, Sony, Microsoft, even Tesla are correct in limiting options on their platforms, however we as consumers have a choice to buy other products.