Except that they didn't. It was nothing to do with Nissan. Haller and Schuller had got hold of an ex-Works circuit race car from South Africa (where it had been left behind by the Works team in 1973 with the intention of allowing a pair of local drivers to compete in remaining rounds of the Springbok Series, only for the series to be cancelled due to the Oil Crisis...) but it was not authorised by Nissan and they had no direct factory support. And Nissan were not happy that privateers were entering an ex-Works car at such a prestigious race. The car just wasn't suitable and, in Le Mans 24hrs terms, Hallers team was a shoestring effort.
Easy for you to say now, but this was a period where such races did have participants who were - let's face it - out of their depth. Haller and his team had an opportunity (they only just squeaked into the starting line-up through the non-participation of other qualifying cars) and they took it. They were attempting to punch above their weight, but hampered by lack of replacement/spare parts and - ultimately - full knowledge of the details of the car. This was a rather special piece of equipment, but they had not built it and they had only limited knowledge and limited spare parts. They were doing as best they could manage.
Despite their troubles, they were classified as finishers in '75. This allowed them a smooth entry to the '76 race, with the car rebuilt/refreshed, but still - inevitably - a lack of spares and running on a limited budget. It was to end in tragedy.