Can anyone explain what this is? I'm wondering if it's only suitable for T1's who use a pump.
Yes, it is only for pumpers. You turn your basal delivery off or down for a few hours and then you add the insulin lost from the basal on to the meal time bolus so all the insulin is working straight away to deal with a high carb meal, but, because you have turned basal off/down, you avoid a later hypo. It's a fairly high maintenance technique to be doing often, because there's maths and buttons to press to turn off and back on etc, but apparently it's popular with pregnant pumpers where the post prandial targets are much tighter.