Remove Messages feature is confusing

### Steps to reproduce

Apologies if there's already a ticket for this, or if this should be split, I couldn't find one in the element-web repo at least. I think having a ticket for the remove messages UX itself would be nice at least, so this aims to be that.

I'm a mod in a public open source related channel that's hosted on matrix.org. Someone set up a bot to bridge the room to an IRC channel. Someone on the IRC side started spamming like crazy, resulting in ~500 messages (I think) on the matrix side very quickly.

I removed the bot user and tried using the "Remove messages" button in element (the desktop app) to remove all recent messages of the bot user. In the order of my experience using this feature

- Nothing seemed to happen, ie there was no feedback or progress indicator of messages being removed
- Trying again after restarting, I got to remove some messages which seemed to disappear. I waited a while, restarted element, all the messages seemed to still exist
- Pressing the "Remove messages" button seemed to give me varying amounts of messages I could remove, sometimes more, sometimes less
- I had tried sending a message to the room about the situation, which failed to send. Trying to retry or delete the message would make element freeze. (at least, I think it was related to that unsent message)

I then tried the same via app.element.io. Now all messages are *seemingly* removed immediately, but when I open the room in element X I see that the messages are actually being removed one by one, with 1-2 seconds in-between each message. At this rate I assume it'll take a few hours? Can I close element while this is ongoing? The UI for "Remove messages" told me to not "refresh" my client or something similar.

Edit: Thankfully it didn't take multiple hours in the end.

### Outcome

#### What did you expect?

I expected to be able to remove all recent messages of the user in question immediately, in bulk. I expected the UI to show me the real actual state, ie the state also experienced by other users in "real time". If all messages cannot be removed immediately, I expect a progress indicator of some sort and information on whether or not I can close the app while the removal is ongoing.

#### What happened instead?

The above. Overall, having no prior knowledge of this feature or having used it before, I'm not sure whether I can close element or whether it's manually sending requests to delete messages one by one in the background and so I need to keep it open.

Element gave me the impression that all messages were already removed, but looking checking the room from element X I get the impression that this is not accurate.

### Operating system

_No response_

### Application version

_No response_

### How did you install the app?

_No response_

### Homeserver

matrix.org

### Will you send logs?

Yes