I think it depends on the hose ends. If one is not pressed on, then it should be fine. Shimano would have to be a bit silly to do this both ends unless they only produce a set number of hose lengths.
The very early ones have the brake hose exiting the brake lever at 90 degrees so have a banjo fitting. So i think that is pressed on. You would buy specific hose lengthwise, so yes, shimano were that silly.
Ignore the above. You can do either end to shorten. I have done a few sets of Tech 2 M4 and a couple Tech 3 E4 and it is easy. I usually put a surgical glove over the end with the insert on to pull it off in case it flies off so that the glove catches it. Watch this and it shows how easy it is.
