Let me correct you. I have no idea who come up with this nonsence but it is not true and that CPU switch thing does not even make sense. It is all right I just want to make things clear and right.
SFP wasn’t “supported” only quite early in the development process od 4.0. The automatic SFP and metalic switch is not supported. You have to switch it manually by relinking devicetree link in /boot. This is fixed on Omnia 2019 already by new uboot and will be fixed on rest of them once we update uboot on all of them with future update. Non the less SFP works. You might just have problems with some modules as support is now fully done by kernel and not by userspace utility now.
There are two ethernet ports going to switch chip. Both of them are accessible trough both of the CPU cores. The problem is that DSA that is now used by kernel to automatically manage switch chip and it in its design supports only one link between CPU and switch. Most of the users won’t notice any change unless they use that second line as deditated gigabit connection. This was also “fixed” in one of late betas and now second link is used for Lan4. There are plans with upstream to make that configurable (moving lan ports between eth0 and eth1).