I do not believe that it is abnormal this year. I suspect that the T20 schools are expecting a higher yield this year as some candidates that in other years would have chosen a cheaper school or one in a more desirable location will choose the higher ranked school out of a concern for the new P/F nature of Step 1. Therefore, out of an abundance of caution, the T20s may be parsimonious in extending offers of admission. After the dust settles, some may find that they underestimated their popularity and they will then carefully fill from the waitlist. Be patient. You won't go 0-6. Please, keep us posted.