What does Converting (forward) mean in diskutil?
Converting &quot;forward&quot; means that direction is from not encrypted -&gt; encrypted. I.e. you started with a blank disk and enabled encryption.
It is possible to do a conversion in the opposite direction if you later decide you do no want your disk to be encrypted.
Your backup was encrypted - it is not stored in the clear when encryption is enabled.
Encryption does take a long time, yes. It is intentionally throttled to not consume system resources, but takes place in the background. You can keep using the computer and the disk while it is working.
It can be a pain if you're encrypting an external disk and need to keep it connected for a long period of time, but unfortunately that is normal.