It seems somewhere along the line the developers have fixed this "cheat" so the only way for this to work is to downgrade the game version. For that we need to do a couple of things:

For this you'll need to have Steam running before proceeding. After that you can just hit Windows key + R (or open the "Run" app) and type "steam://open/console" as seen here:
This should turn visible a new tab on your steam application, as seen here:

To download an older version of the game you need to know three things: App ID, Depot ID and the Manifest ID. If you want to skip how you would find this out for yourself just go to step b) and use the same command I did which should work. If not look at step a) to see how you can choose an older game version.

For this you can use steamdb.info You can find Coromon information here:
https://steamdb.info/app/1218210/
As you can see in (1) the App ID is "1218210". Next we need the Depot ID so click on (2)Depots.
From there you can see the DepotID we need is "1218211" so click on it and then on "Manifests".
Now you will see a list of all the game's manifests sorted by date. We just need to pick one to revert back to. I am not sure when the "cheat" was fixed so at first I picked one that was quite old, from July 2022 and verified the "cheat" still worked. However it seems from that time the achievement itself doesn't unlock, but thanks to input by users KOKOC and Siçrav it seems with manifestID 212099964759484703 from 10 February 2023 the "cheat" works and it is possible to unlock the achievement. So a big thank you to them :)

Now we just need to go to the "console" tab on our Steam application and type:
download_depot <AppID> <DepotID> <ManifestID>
Which in our case is:
download_depot 1218210 1218211 212099964759484703
After a few seconds you should see "Downloading depot 1218211" like in the image below.
This download actually took a long time for me, don't know if it was my internet connection that was poor, but it took about 40 minutes. Hopefully for you it will be faster. Either way once it finished it should show "Depot download complete".

Now that you've downloaded the older game version you need to copy the files you downloaded and overwrite the original ones. For this you need to copy everything you downloaded which should be in <Steam install path>/steamapps/content/app_1218210/depot_1218211. As seen on the image.
So copy everything on that folder and then paste it on the Coromon folder. Which should be in <Steam install path>/steamapps/common/Coromon. Like so.
After you've overwritten the game files you are almost done. One last step is to just right click Coromon on Steam and choose "Properties" and then "Updates" and change to "Only update this game when I launch it". This way you should be notified if you want to update the game or not.
And that's everything. At this moment you should have a Coromon version installed that let's you use the cheat below so just continue with the rest of the instructions :)

Small heads-up this was done in Windows have no idea how to do it in other OS.

1) Start Coromon and go to the start of the mini-game.
2) Hit Ctrl+Alt+Del, choose "Task Manager" and go to the "Performance" tab



3) Then click on the bottom where it says "Open Resource Monitor"

4) In the overview you should be able to find "coromon" in the list of processes running. Right click on it and choose "Suspend process".
5) A new window will popup and now this part is a bit tricky. Basically you have to click "Suspend Process" while your swurmy is in the air in the game. What I did was align the windows as seen below, hit space a couple of times so that the swurmy would be the highest up possible and then quickly change window and hit "Suspend Process".
6) Now you will notice that the game is frozen, but the fact of the matter is that your score is still counting, even though it is not refreshing. Just leave the window frozen for about 2 minutes. I left mine a bit longer (2 minutes and 30 seconds) and when I unfroze it the score was 706 as seen in the screenshot above.
7) So once the time is up go back to the "Resource Monitor" and just choose "Resume Process".
You will see that your score is now over 500 and the achievement should unlock. Cheers.