More infromation about why metamask-mobile does not inject "ethereum" into iframes

### What is this about?

Hello,
I'm currently working on an NFT project, we offer integrations through iframes.
I noticed that metamask-extention injects window.ethereum into both the parent and iframes, but metamask-mobile does not.

I did reserach and found that support [was indeed added in 2019 ](https://github.com/MetaMask/metamask-mobile/issues/1154) but then [removed a year later](https://github.com/MetaMask/metamask-mobile/commit/0351a3e81c0a422485da80954ca1b4276700c04d) for a reason that I cannot find anywhere.

I was wondering if you could suggest a solution and if not, explain more in technical detail what the reason for the removal was

### Scenario

_No response_

### Design

_No response_

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### References

_No response_

Start with the linked 2019 issue and the referenced removal commit, then compare the documented iframe injection behavior of MetaMask Mobile and the extension. Done means recording a maintainer-confirmed technical reason for the removal or a supported solution for iframe integrations.

Written by the indexing model from the issue text.