That's not how alternate modes work -- there isn't really a "standard" mode. When you plug in a Type C cable the two devices negotiate (via a combination of passives and some active negotiation) what protocols you want to use. Yes protocols with an "s." Power and, say USB 3.1 v2, or power and TB3 or HDMI or whatever.

Among the problems is you can have a cable that can't support a particular alternate modes, or can't support adequate power. The USB-IF hasn't defined a set of standard icons (not that there's much room for them -- they'd be microscopic).

Also the MacBook Retina has USB 3.1 v1 so supports just ordinary USB 3.0 & HDMI. The MacBook Pro supports several more alternate modes.

At least to Apple's credit, AFAICT all four USB ports are identical. Even that isn't required by the spec.

I read that the 2 ports on the left and right are actually slightly different. I don't recall exactly what it was but I think it was something about Thunderbolt 3 because of a lack of sufficient PCI-E lanes for all four ports.

Official Apple comment:

  The two right-hand ports deliver Thunderbolt 3 functionality, but have reduced PCI Express bandwidth [1]

The full Thunderbolt 3 speed is 40MBPs (use the left-side ports to achieve that).

I can't find any official document which clearly states the speed of the reduced-functionality ports, but Apple also state this:

  All late-2016 MacBook Pro models deliver USB 3.1 Gen 2 (10 Gbps) performance on all Thunderbolt 3 ports [1]

So there may be a 4x speed differential, depending which port you plug into.

[1] https://support.apple.com/en-us/HT207256

Interesting. Sounds like they prioritized standardizing the connector but not the rest of the details.

Perhaps in the scope of large scale manufacturing, having multiple (redundant) connector styles is a low hanging fruit for cost reduction.

But it seems that there would be increased user confusion and technical support required. Very strange.

  > "they prioritized standardizing the connector but not the rest of the details"

In this case, "they" are the "USB Implementors Forum (USB-IF)" [1], rather than Apple. It's the USB-IF who agreed the standardisation of spec, but permitted the potential for "alternative mode".

Apple might have taken advantage of it, but it's the USB-IF who decided to make the standard rather more variable.

[1] https://en.wikipedia.org/wiki/USB_Implementers_Forum