It says so on the description directly next to the name: "Transitional package - chromium-browser -> chromium snap"
There only for people upgrading, so they are not suddenly surprised seeing their browser gone.
Mixing your distribution systems with references to each other seems like a recipe for confusion and anger. And it looks like they got the expected outcome.
I mean: clearly some people do care, given that that this thread exists. I think you'll find that they aren't your typical Ubuntu user though.
Users who do care are quite capable of adjusting their configuration, and Ubuntu doesn't get in the way of that (configure apt not to install snapd ever, and it won't).
This is only an issue for users who want to push their political opinions on to other Ubuntu users.
People where "suddenly Chrome is gone" will be angry too.
Just imagine the outrage of a title like "The update to Catalina wiped all mac users' browsers with all their bookmarks and history. Forever".
And those are the people that cannot easily solve it. The person being able to know what a "Transitional package" or the difference between snap and apt is, is also the person who knows how (to google for) to move the old ~/.config/chrome/ directory into the snap.
This is also the person being enraged that Ubuntu offers a mechanism for all the people who cannot do that themselves. That sounds quite selfish to me.
Worse. Because when you then search the "software store", and install chromium, all your bookmarks, history, forms and other state is lost. At least the "apt package" migrates that for users.
For Ubuntu 20.04, it has been explained (in 2019!) that Chromium will be only available as a snap package. To help users transition, the command `sudo apt install chromium-browser` would install the snap package. It is better than "package not found".
It is so simple, but if you are stuck in a negative sentiment on snaps (read this thread), you get crazy.