Yes, but a GoLight ticket is also flexible, so there is no need to buy new tickets. Its just not flexible for free. The only difference with Flex is that there is no ~60 euro penalty to change flights.

However in that way it also makes sense to not allow the 'upgrade', as the fare difference between GoLight and Flex is less than the 60 euro change fee. And like you said, somebody requesting this change is very likely to want to change the ticket.