Unlike other special objects, like Live Paint-s, Envelopes, Blends, etc., Intertwine objects don’t have their own Expand command. It’s not very consistent.

We need this command to appear in the menu, the context menu, Properties, Control.

Repeats don’t have this one too, which is also strange: https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests/suggestions/41138800-repeat-expand-appearance

We have to use the general Object > Expand: Object for this — but is has a dialog, which is not always nice.
A specific Expand allows to choose the order of operations for a complex objects. Take blends, for example — if you apply 'expands' in a wrong order, you risk to expand the content first, and get a wrong blend between already expanded objects.

Yes, there is another unintended workaround, — apply any effect and get it expanded on its own (https://illustrator.uservoice.com/forums/601447/suggestions/45845533), but this is not how it should work!