While endpoints may be cached, you may also hit a server that doesn’t have cached results. You may see something like this if you poll frequently:
Request 1: 1000 followers <- Original cached request
Request 2: 1020 followers <- Second request by you that hit a new server, lots of new followers
Request 3: 1000 followers <- Original server
Request 4: 1015 followers <- Someone else made a request and you hit their cached server
Request 5: 1020 followers <- Your cached second result