OK I will try to explain:
Onkyo chose a chipset that is HDMI 2.0 and has HDCP 2.2 on two of it's ports. Samsung also made this choice on the MHL port. This chip set is only capable of the same 4K as HDMI 1.4; Meaning 4k 24/30 at 4:4:4 and 4k 60 at 4:2:0.
Denon, Pioneer, Marantz, Yamaha, etc all opted for a full speed (18Gbps) HDMI 2.0 chip set without HDCP 2.2 (it just has the standard HDCP everything has). This allows full 4k pass through as well as full 4k 60 4:4:4 upscaling.
Both are a gamble since there aren't really any HDMI 2.0 devices and HDCP 2.2 hasn't been implemented in anything yet. The thought process of Denon and company is rely on the TV manufacturers to deal with HDCP 2.2 and run two cables, one for audio and one for video.
Samsung has the best strategy in my opinion with the One Connect for upgrades as standards change.
UN65F9000AFXZA + SEK2500U/ZA firmware version 1162.2
Denon AVR-X5200W, Apple TV, Sony BDP-S6200, PS4, Xbox One
(2) Klipsch RF-82IIs, (2)RS-62IIs (4)RS-52IIs, (2)RS-42IIs, (1)RC-62ii, (2)RB-61IIs
(1) SVS PB12-Plus, (1)Emotiva XPA-100, (1)XPA-200, (1)UPA-200,
UN55HU8550, AVR-S900W, Ceton Echo, Apple TV, Panny BDT460, PC,
(1)Klipsch G-42, (2)G-16s, (2) Bose 161, (1)BIC Acoustech PL-200