Do we have a "reconnect strategy" in File inbound endpoint? I don't think as it has only on the FTP connector. But the article screen showed that it's available.
For Mule 4, it does. You need to configure yourself. Both the link you shared and official documentation says you can configure reconnection strategy for file connector: https://docs.mulesoft.com/connectors/file/file-documentation#Reconnection
As far as I know, all connectors are derived from the same interface and support reconnection if applicable.
I recommend you to depend on the official documentation for these cases.
For mule 3, you should look into "File Transport" which is based on polling: https://docs.mulesoft.com/mule-runtime/3.9/file-transport-reference
It doesn't support reconnection and if you look at the source code, you'll also see that doConnect is not implemented since it is poll based: https://github.com/mulesoft/mule/blob/5ed22e1e60f584ea8f301ae5ffb16e5c0c5e25c1/transports/file/src/main/java/org/mule/transport/file/FileConnector.java#L299