It does not mean that lemmy is less secure, but yes, it means that malicious app developers will have a much easier time stealing login credentials because entering them inside the app is already the norm. However this is definitely a feature that can be added so it does not mean anything bad long term
Also, as the developer of Lemmios, it is somewhat negligence on my part (not saying this is true for any of the other app developers, just me), we all google when we code and generally the newer features make things much easier so it is really hard to google older features since they are harder to implement and get quite buried. I also think for me at least my apps start as passion projects I don’t really expect anyone to use so I forget that iOS versions under my current one exist lol, it’s a lot easier to start on 16.0 and stay on 16.0 forever than go lower after the project has started, sorry.