Not that I'm absolutely sure, but I think there are two reasons:
1) The pack was already fully charged, so basically a re-peak is overcharge.
2) By discharging a little at first, you start to warm up the pack. After the small discharge, you aint over-charging and the pack takes much more milliamps, than if just re-peaking, thus this will also make the pack warmer. And packs just perform better, while warm. Reason is, that warmer means lower IR.