Luzon Grass Dart

Yesterday morning, when I was taking some pictures of a Taractrocera l. luzonensis - https://www.projectnoah.org/spottings/1130305490, my wife who was just a few metres away called out to me "There is another one the same over here". So, I went over to have a look and was immediately captivated by the specimen which is now the subject of this spotting. The first picture shows what got my attention. It was not standing in the usual posture that is normally adopted by these skipper butterflies. I have only ever seen two postures in the Hesperinae. One is when it flattens out its hindwings and holds its forewings up at an angle, but not closed (you can see exactly what I am talking about in my last picture). This "posture" is adopted when resting. The other posture occurs when it unrolls its proboscis to sip nectar, the wings are all closed together vertically (I didn't get a picture like that in this spotting, but I am sure you are all familiar with that posture). However, if you look at my first picture, you will see that this little butterfly is crouching with its abdomen flat down on the leaf, its legs all flat out and all four wings almost flat on its back in a moth-like position. I have never seen anything like this. It reminded me of a kitten flattening itself down in preparation for a playful attack on one of its siblings. I was lucky to get a picture of this because the butterfly "stood up" properly, a second or two later. I watched it for a while, but it showed no signs of returning to that unusual posture. I can only put it down to some kind of aberration which I will probably never see again. I did not notice at the time, but in the photo, the proboscis was deployed. Had it taken to that position to sip something that was hard to reach? But I had better not start guessing. It is probably better to wait for some level-headed lepidopterist to provide a perfectly good explanation :-)