Not so. The burnings happened. Here’s just a couple of examples, there are many more:
“This beautiful church was built in 1745 as the church of Prince William Parish. It was burned by the British in May 1779. “
http://www.gloryway.com/old_sheldon_church.htm
“Red House Presbyterian Church... The first building, one of three successive wooden frame structures, was burned in 1781 by British soldiers during the Revolutionary War.”
http://www.rootsweb.ancestry.com/~ncccha/memoranda/churches/redhousechurch/redhousechurch.html
I stand corrected on those particulars. Nevertheless, these were limited examples and not part of a general policy — as the wide scale survival through the Revolution of most colonial era churches indicates.