This issue also repros for non upgrade situations:
1. Sign in multiple profiles and open tabs in them.
2. Shutdown the device, without first logging off.
3. Restart the device and sign-in to the same primary, secondary etc profiles.

I observed the primary profile restored directly, but a secondary profile instead showed the Restore butter-bar, saying that Chrome had not shutdown cleanly.

It's interesting that you observe the opposite behavior from what I've seen in the upgrade scenario.

Yes; now you mention it, I wonder if it's racey, or if they're actually two different issues.

I can reproduce this issue by simply visiting chrome://restart while I have two profiles loaded. Both profiles reload but one of them loses all of its tabs.

Bumping priority based on their being a reliable and simple repro as per #5.

I'm not observing this when I try #2 or #5. The profiles should all have "Continue where you left off" checked in settings right? The tabs are as expected after I shutdown without logout or chrome://restart.

reillyg@/wez@ - can either of you still reproduce this?

I can still reproduce this on 60.0.3112.0. Both profiles have pinned tabs and a regular tab open. If I navigate to chrome://restart the second profile comes back with the pinned tabs and regular tab but the first profile only comes back with the pinned tabs.

Hey Reilly,

I tried pinning the tabs but I still cannot reproduce. I'm on 61.0.3123.0. When you have time, could you check if it works on the latest?

Thanks,
Sammie

I flashed a device with 61.0.3123.0 and confirmed I can still reproduce this.

Sammie pointed out that the device I'd flashed 61.0.3123.0 onto had my first profile set to "open the new tab page." The device I originally encountered this issue on however is set to "continue where you left off." Flipping this setting to "open the new tab page" and back to "continue where you left off" fixed this issue for me.

wez@, can you confirm that this is the case for your system as well?

I'm away from the device right now, but will try when I'm next in front of
it.

Can you clarify whether you mean flipping the setting without restarting,
versus flipping it, restarting, flipping it back, and restarting again -
i.e. you'd also have lost any existing tab/session state?

I flipped the setting without restarting so I would not have lost any existing tab/session state.