The server lifts up the bottom of the priest’s chasuble on two occasions immediately after consecration to enable the priest to more easily raise up high, the precious host and blood respectively. In the past often the chasuble was quite heavy and it was in a sense a necessity to have the server’s assistance in this way - it has continued as a part of the ritual even though the chasuble is usually now not so heavy as it often would have been. While custom may vary from place to place, in my experience it is unusual for there to be a solita oscula when the server lifts the chasuble.