The current oncalls at the moment on the chrome waterfall
https://ci.chromium.org/p/chromium/g/chromium/console

are listed as follows:

Chromium
<none>
Android
<none>
iOS
<none>
CrOS MTV
<none>
CrOS non-MTV
<none>
ChromeOS Gardener
<none>
GPU
<none>
Angle
<none>
Perf
<none>
Perfbot
<none>
V8
<none>
Trooper

The calendar does show assignments, so this is definitely an error.