Is this a one-off change, or happened substantially over a period of time?
For the former, it could be last-minute equipment variation which happens all the time, and is perfectly possible to happen in the opposite.

If LH is to combat with UA (although I'm unsure how this works under the Star Alliance trans-Atlantic joint venture), the Allegris deployment will be permanent (or at least a fixed period of time); afterall, UA Polaris is probably superior to LH's old Business Class, at least in terms of layout