maybe your machine, (i.e power supply unit)
has this ability to only occur during "ramp up" or innitial starting of the weld, so that it can make the heat zone narrower and more directed and thus will not overheat a larger area.
kinda tied into the ability of the power unit to start at a certain percentage of what your maximum power/voltage is...when you innitially depress the pedal.
at least MY UNIT has that option, so that I can in fact have max at example 200 ....and the innitial start power when I first depress the pedal can be as low as 20 percent of the maximum...so that would then be 40 number.
but when it is at the 20 percent number, the power /flame/heated zone will be NARROWER and thus will be also more directed.
this allows the centered /directed heat to not burn off when you are doing inside corners or directed chamfers within a angle.
I am also one of those that have very good results putting a point on the tip of tungsten when doing aluminum...but only pretty much when under about 250 amps.
preheating aluminum to 150/300 degrees helps a lot.