It's a complete hull and superstructure, I'm sure whoever eventually ends up owning the remnants of the shipyard will eventually complete it or sell it on to be finished in some form, probably with diesel power units instead of Brittany's LNG order. It has to be far more valuable as 75% of a complete ship than as a pile of scrap steel.
IF ordered a high freight capacity ferry, Honfleur was to have several decks less freight and several more passenger capacity. It would be the wrong spec for IF's Dublin-France and completely useless on Holyhead. While it is probably possible to alter it to have more lanemetres there is no way it could be made to match the purpose built capacity IF had ordered.
I can't help but think that the cancellation is as much down to the prospect of covid and brexit causing a long term downturn in business and BF no longer wanting to sink capital they may not have into a ship they won't need for years. Even if they have to write off a portion of the purchase it may be the better choice for their business
I would say that IF may also be very happy that they are getting their cash back rather than a costly ship they don't really need in the current market.