I’ve got a pair of the Cyglove ones, which are fairly good, but the opening to slide them onto the bars is quite large (good) and doesn’t completely close (not so good)
Now you’ve got me thinking mine have the same problem! TBH have not really noticed, but I typically run hot so for me it’s a plus-side to have that ventilation as I tend to have more issues overheating than under-heating. Just took a look, maybe look at stitching some velcro tape (may intefere with volume required for shifter operation), or wearing summer mitts as extra layer?*
*I often wear mitts anyways as depending on wind-chill/wet I sometimes find myself out of the pogies on long sheltered climbs.