As Maura said - riding with hands wide can be a good thing. Particularly on a green horse, you are giving a clearer, steadier contact as opposed to the 'uniform' position of hands together just above the wither. The hands should always come back to the wither when the horse will accept the contact.
Riding with hands low and wide to encourage long and low is simply focussing on the head and neck, and not the hind legs. Just like to multiple questions about collection that get asked on this forum, long and low is still all about the drive of the hind legs into a contact, not just having the horse drop it's head and neck down. Unless the hind legs are still travelling through and under the horse's centre of gravity, there is little to no benefit of the exercise as you are merely teaching the horse to travel on the forehand. Long and low in it's genuine form is intended to stretch and lift the topline. This will not occur if the hind legs are not working.
So many people like to 'boast' that they warm their horses up in long and low to let them stretch. You then see video's of these warm ups, and they are doing nothing at all other getting the blood pumping, the back is stiff, the hind legs are a mile behind them and usually the nose is curled slightly under due to the use of reins to create a low 'head set'.
When I warm my horses up, I prefer to ride in quite a long 'frame', with the horse slightly above the bit, and just focus on reactions to my driving aids, while ensuring that I can move the jaw and neck where ever I want it.
Then I will refine it, until I am starting to get a connection over the back, the jaw and poll are soft, and I can start to move the shoulders and quarters around. Only once I have the horse's back, and can feel that I've got a connection with the hind legs, will I ask the horse to come lower and stretch towards the ground. The second I lose the back and the impulsion, I bring the horse straight back up, re establish the connection and activity, before asking for the stretch again.
Long and low is more complex than what it is made out to be!