In this situation it makes perfect sense that UA would count the miles, as UA gets the ticket revenue once they lift the LH coupon. However, if it is a LH flight number on UA metal the answer may be different, since then UA doesn't keep all the revenue, since you are booking into LH's portion of the seats.

I'm also surprised to hear UA doesn't count flights on LH transoceanic flights, since UA/LH have a revenue sharing agreement. Thus, UA doesn't really care if you fly UA or LH over the ocean, as the ticket revenue is the same.