The disadvantage only holds for the Gribeauval 6.4in Howitzer and possible the Longe Porte Howitzer. The AnXI Howitzer that by 1812 was in universal service with the Longe Porte restricted to the 12-pdr batteries and the Gribeauval 6.4in howitzer retired from service. Most were out of service by 1807.
"The French howitzers could fire at higher angles and achieve targets at longer ranges."
The Gribeauval Howitzer could obtain higher angles but not linear range. This is referring to the range tables that I have.
You observations upon the Russian guns are facinating. Thank you as there is so much for me to learn.