(For future reference, steps to reproduce would be welcome.) I go to https://calendar.google.com/, go to "Other Calendars" in the sidebar, click the + button, select "From URL", paste https://static.gnome.org/calendars/schedule-unstable.ics. Indeed Google does not display anything.
Manually importing that file into Evolution displays events as expected. Throwing that file into https://icalendar.org/validator.html it says Success! No errors found.
@oholy: Please report this bug to Google, unless there are any hints that the file is invalid.
What project should we re-assign this to?
In theory that's https://gitlab.gnome.org/groups/Teams/Releng/-/issues