Yes across all devices (mobile, PC, etc.). If it's a performance issue then it's one of those "happy accidents" that is a bug in their favor. Either they don't care about quality or they really like money more than quality, but no reason it can't be both.

Super long chats are slow and sluggish too at least on chatgpt/claude.ai; even on a semi beefy machine.

I’m sure it’s lowkey intentional, probably encourages users to spin up new chats; hence less context.