Yes the Linea Scyon boards are all 4.2m lengths but the ends are supplied with tongue and groove. As the end to end joints are made, one fills the groove with sealant. This ensures the joins are water proof.
The down side is off-cuts typically cannot be used because they don't have the tongue and groove anymore. (except where they butt into a corner flashing)
The joins are visible if you look closely for them but I widely staggered all my joints. (one does not for example join them all in the middle of a wall.)
I used proprietary aluminium corner and window flashings made specifically for the linea scyon cladding . Some of these flashings have complex cross sections because they both make the corner water proof and also hide the end of the scyon boards. These flashings only came in one length so there was some wastage (I could not reuse any off cuts).
Some of the corner flashings require a double stud underneath them. Unfortunately I did not realise this when I made my wall frames so there was a bit of extra work in removing noggins and inserting the extra studs.
I installed the windows at the last minute as I clad the wall around the specific window, so this allowed me to install the windows and flashings in exactly the correct position.