Why does the fibreACE card have a "convert" option?

If the built-in gigaACE ports have to be used to connect a MixRack and surface, wouldn’t an outboard converter box be better since that wouldn’t take up a slot? If the built-in gigaACE ports don’t have to be used, why bother with the conversion and jumper cables at all?

For those who don’t know what I’m talking about, see page 3 of https://www.allen-heath.com/media/fibreACE-fitting-note-AP10843.pdf

The convert modus is that the build in giga ace can be converted to fiber.

This is a cost alternativ.

The primary surface must connect to the built in GigaACE ports.
A FibreACE card in a slot is a different logical set of ports so you can’t connect the primary surface to a card configured in a slot.
To connect the primary surface via fibre you need to use a media converter for the onboard ports and this is the option A&H have given you with switching a card to convert mode.
It’s a useful option to have in an emergency but if you’re planning a system the TP Link converters that Showtime refers to do the same job for a fraction of the price and without chewing up a card slot.
I use the MC220L versions which have the advantage of being able to swap out the SFP+ laser module so you can switch between single mode and multimode should the need arise, again these are a fraction of the price of a FibreACE card even when you take the cost of the modules into account.
The card option is neat if you need to make a GigaACE connection over fibre to a secondary surface or another mixrack but this can also be achieved with media converters and a copper GigaACE card for less money at the expense of a couple of extra small boxes to deal with.
Additionally I think you should be able to connect a dLive GigaACE to other A&H console SLink port over fibre using media converters, I don’t think you can do that with the FibreACE card.

In short the cards are a nice idea but they are just too expensive, there are cheaper ways to achieve everything they do.