[EE]: considering charging capacitor losses. When a charged cap charges a discharged cap.

When I was at TAFE (not sure what the equiv but its below Uni), a lecturer
made an off hand comment about when charging one capacitor from another
that the math does not work out and may have continued to say only half the
energy remains.  My son is now studying simiar subjects which we have
discussed and has renewed my curiosity, so I have finally after 30+ years
decided to get to the bottom of this.
A simple google search yields a formula where the energy is shared between
the two which conflicts with there being energy loss.
Using more specific searches results in half the energy is lost when
directly charging and can be reduced using inductors and diodes.
Asking why half results in some answers restating that half is always lost.
Not helpful.
Others state heat, but does not explain why half.

I think (and curious what others have to say) the statement should be "When
direct charging a capacitor a *minimum* of half the energy is lost and can
be explained considering *Maximum Power Transfer Thereom* "

And I am guessing the issues my lecturer  (and now including myself) was
having with the math was when considering an ideal capacitor.

So what happens here? As the capacitors tends to ideal, the loss of energy
remains fixed at 1/2 *but* then jumps to no loss if we consider a
theoretical ideal capacitor.

That does not seem logical.

Maybe the question lies in the same realm as "does current flow thru a
capacitor?"

If I was near a pc I would try to ltspice it.

Thoughts?

Justin