Main Sequence stars define a particular 'track', on the HR-diagram, with a well-defined slope (log(L) ~ 7 log(T)). However, M-class red dwarfs diverge off-track, 'dipping down' to define a new 'track', significantly steeper (near vertical), for Flare Stars & Brown Dwarfs:

Then, the 'Flare Star track' smoothly 'flattens out', merging into the track for Gas Giant planets:

Thus, if Brown Dwarfs represent semi-fusioning 'super planets', then M-class red dwarf 'Flare Stars' represent the transition, from the 'planet track', to the full-fledged 'star track'.

Now, the 'Flare Star track' is extremely steep, such that increases in star mass manifest almost entirely, as increases in star size (radius), and not star surface temperature. Perhaps, then, with the onset of full-fledged fusion, in the lowest mass, M-class, red dwarf, Flare Stars, their ferocious atmospheric convection currents constantly dredge deeply into the interior, all the way to the fusing core. There, more mass means more fusion, and so stronger convection currents -- which carry away the core heat, 'gusting' farther out from the core, where, when those currents reach the star surface, they erupt out as fierce flares. Yet, for some reason, the "same H->He fusion always operates at the same temperature, which is carried to the star surface, again at the same temperature, albeit having been blown farther afield, radially away from the cores, which are more massive and fusing fiercer" ???

Something 'significant', and 'structural', seems to happen to 'big balls of gas', as they increase in mass, from '(super-)planets', to fully-fusioning 'stars'. Such seems associated with 'Super-Flare' activity, representing the most visible, highest energy examples, of those stars' atmospheric convection currents (ones which "convectively rise, all the way to infinity").