Subtrims or trimmers?

Hello,
Could you tell me how the subtrims work in deViation. I tried them and I feel that there is no difference with the Trims. Yet I have seen on the internet that Futaba subtrims work differently from JR / Graupner / Spektrum subtrims. Is deviation a third functioning?

Hello FDR,
Thank you for your answer. I asked this question because when I look in Mixer output and I also control servos and the neutral point of the servos, the action of the trims and subtrims is identical. I put -30 in subtrim and I compared by setting the trim fully set to the step of 0.1. And the servo neutral moves in both cases at the same place and I have the same races on one side and the other of the neutral. I took a simple, unmixed channel with a 1-to-1 curve.
I tried with a RX DSM2 and DEVO and I have the same result. Frankly, I do not understand! For me I think the trim works properly, but not the subrim. What do you think ?

I understand your answer. I enclose a little diagram that I found on the internet. Finally, I do not know enough to say what is best, but I wanted to understand that deViation. Is this a disadvantage or a benefit the real subtrim?
Thank you very much for everything.