I think the rationale is: You don't want to be holding an asset who's value is predicated on a very low interest rate loan. If mortgage interest rates go up by a factor of two, housing affordability will come down by a factor of two (assuming an interest only loan). Better to sell now, pocket the money, then buy back in when prices are lower.
On the other hand it is buying low and selling high. It's a fool's errand to try and sell at the exact top (or buy at the exact bottom), but if you're already up nicely you have done the hard part.
