I noticed that 15w43a changed things so lily pads may now be placed on ice and frosted ice, presumably so Frost Walker won't go wiping out lily pads all over the place. Sugar cane received a similar treatment, it won't break if its adjacent water block is turned to frosted ice.
But if that was the intention, it's flawed since lily pads will still uproot if they receive a block update when on ice or frosted ice, including the update triggered when Frost Walker freezes the water block.
Confirmed.