Race cars with sequential shifting dog boxes use the clutch just once or twice and that is to pull off from stand still or to come to a full stop.
Most sequential systems (BTCC, WTCC, Clio Cup, Porsche Cup, F1, F3 etc etc) use a electronic shifting assisted "dog box", the gears are none helical, they are straight cut and do not rely on syncros. The gears are 'pushed' in to gear, normally this shouldn't de done on full throttle as the force required to change gear is too extreme for the driver and the gearbox, flat foot shifting wil sheer teeth off of the dogs in
most none syncro transmissions.
The majority of modern sequential gearboxes are electronic assist, at each UPWARD gear change engine ignition is cut for 0.1-0.001 seconds (depending on system and car) thus 'throttling off' and allowing the driver to sit flat footed on the throttle - it sounds like a full throttle gear change but it isn't!
On DOWNARD shifts the electronic system also blips the throttle to match revs for the lower gear thus allowing a quick and clean downshift without the aid of syncros OR driver input - these systems do remove a certain element of skill from the driving but are also the most widely used and mechanically safest.
I personally find the 'auto-clutch' setting the most authentic in that you have fully assisted gearchanges and should never been using the clutch.
In fact, in real life, using the clutch for gearchanges is more dangerous and runs the risk of damaging the dog teeth - the reason for this is that a human is much too slow and the process of engaging the clutch, changing gear and releasing the clutch takes too long, the electronic sensors, cuts and blips work much better!