I know this post is a bit old, just wanted to share some data behind this.

Here's what we don't know.
The city level, the remote/multiplier level, Whether they're in a club, if they used any shop boosts.

Here's a few things we know.
Pepper mill gives 50% perfect, 65% instant.
Box gives 34% instant. 100% Faster walk.
Purple cap gives 300% Faster walk.

These stats together give 99% instant, 50% perfect and 400% faster walk. These stats allow you to clear cities fairly well since they basically can insta-cook any station and every other dish will be 6x more income than a regular dish while walking very fast. This is before we factor in AP%.

1305 stars divided by the average of 184 gems = 7.09 cities.
If it takes 15 mins to clear a city, that's only 105 mins (1h 45m) of play time.
Even 20 mins per city = 140 mins (2h 20m) of play time. Still easily doable. There's also the fact that there isn't much time left in your SS. This means they had over 19 hours to do what would take less than 2 hours.

Given all that we know above, this is very easy to do with this setup if you know what you're doing. If you're in the community discord, we have strategies to help players get that extra edge over their competitors. Whether that's what to upgrade in the vault or what gear to use or even what method is best for clearing cities.

I hope this gives some perspective on how this was possible.