"Last seen" date for contacts is not accurate
When using TELEports, the "last seen" information in my contacts is not accurate; it usually reflects a very old date.
When on-line, those contacts still appear as "last seen x.x.x" when the desktop version and the web version of Telegram show "online" and a green dot.
This happens with those that have this info public (not with those that have this data hidden, obviously).