Preturbing Admirals being bad generally, too. (Worse than swans, really<g>)
But, in wartime, the bootstripe would sometimes be larger than in peacetime, if my memory serves. Wider stripe means that harbor does not have to be as calm to apply hull paint, especially when using hanging planks. Slightly more work if using punts/flats along side.
Boot topping (alternate terminology for boot stripe) also sealed the edge between copper-containing bottom paint and the "ordinary" hull paint.