You select chat A, you scroll to somewhere, you switch to chat B then you again switch back to chat A. And chat A is on the same position as it was before the switch(es). There is also a Setting/Preference to turn this feature on/off.
When you switch between chats, each chat appears at the last message.
seems not to be that clear when looking at other apps. eg. Telegram remembers position - while WhatsApp and Signal behave like Delta Chat, so do most mobile apps. probably to avoid confusion and to have a always same, working path.
so, not sure, if that is an unconditional improvement. i never have seen a real issue here. if you scroll to find sth. important, you eg. can always save to “Saved Messages” and there is the search.
but let’s see if others chime in here.
for an option: well, we usually avoid options wherever we can. and for this level of detail, that seems not fitting. if we decide we want to go for it, it seems easy enough to use the scroll down button