No?
At maximum range (35), the Rifle's Garand has ~1.7dps, the M1919 has 8.76dps
4 x 1.7 + 8.76 = 15.56dps at 35 range
At maximum range (35), the Gren's K98k has ~2.26dps, the LGM42 has 8.93dps
3 x 2.26 + 8.93 = 15.71dps at 35 range
Riflemen have 5x 80hp, or a 400hp effective pool
Grens have 4x 80hp, or a 320hp effective pool
400hp/15.71dps = 25.4sec
320/15.56dps = 20.6sec
Rifles at max range w/ M1919 are 19% stronger than Grens w/ LMG42.
This doesn't take into account that for each model lost, grens lose 33% of their K98k damage, vs. 25% for Rifle's Garand. Also note that this becomes more in favor of Rifles the closer you get: The LMG42 stays around 0.2-0.3dps ahead at all ranges, but the 4x Garands fill in that DPS difference at range 25. On top of that, Rifle's have far, far better vet bonuses.
And what about vet3?
3.369 х 3 + 13.588 (mg34) = 23,695 (max range 35)
2.371 х 4 + 12.291 (m1919) = 21,755 (max range 35)
400/23,695 = 16,8 s
320/21,755 = 14.7 s
The difference in DPS - 14.29%
How much more expensive is the unit = 16.67% mp
How much more expensive m1919 = 16.67% muni
At the same time, m1919 is a weapon from the doctrine.
Given the fact that 1 vet is bad for the rifleman
Given the fact that the target size is very poor 0.97 vs 0.91.
This speaks of large losses at an early stage of the game, and the grenadiers, due to cheap and quick access to mg34, can be much more effective. So the grenadiers gain vet faster. And only on the 3rd Vete, there is a chance to win. Because vet 3 Grens - 0,7 target size, Rifle - 0,64.
Grenadiers are in a better position. Especially when at the beginning of the game they are covered by the best mg42 in the game.
And using your math, you will not hide the fact that the USF is the worst fraction in tournaments. This is the main reason why I discuss it here.