Surely they need the tendrils to climb?
Let me take you back to what I wrote previously;
Obviously if you remove the tendrils you will have to tie the stems in manually with sweet pea rings, twist ties or wind them around a suspended vertical string.
Lets see if I can clarify it a bit better;
The following picture is not ideal for explaining it but it is the best I have;
At the bottom of the picture note the end of a tendril that has been cut off, to the right of it is a tendril that I missed.
Note the green sweet pea ring (higher up) that is holding the stem back to the cane.
I hope this calarifies the situation better.
Sorry I didn't have a better picture example. Obviously when I took the picture I was photographing the flower not the mechanics of supporting sweet pes ;)