High blood sugar causes insulin resistance, but this is very temporary insulin resistance. The job of insulin is to get sugar into the cells. It can only do that from within the cells. If you have high blood sugar the cells are surrounded by a crowd of sugar which the insulin has to battle through to get to the cells before it can start the work of letting the sugar into the cells. As soon as you're euglycaemic and the crowds of sugar are cleared out the insulin resistance will disappear. Instantly
How high are the quite high levels you are seeing at the moment? Have you been given guidance on correction doses?
Your HCPs might be trying to step you down gradually to target range because a sudden change from hyper to euglycaemic can feel pretty unpleasant, your body will have got used to the high blood sugar levels and will, wrongly, think that normal blood sugar is too low so you might get false hypos.
So even though you could give a correction and achieve euglycaemia pretty quickly, that is likely to make you feel rather rough and if you're recovering from DKA you probably already feel pretty rough without throwing a false hypo into the mix. So you're better off gradually stepping down blood sugars.