Not real uncommon to have T-1-11 siding over wood frame without house wrap back then, but it probably should have at least had building paper (felt) installed behind it ("should have" being key).
My house up here is wood frame (1978 vintage), I believe I recall having seen felt when I looked inside the vented area behind the fireplace, 1/2" plywood, then 1/4' or 3/8" cedar plywood with cedar battens on it to look like rough-sawn cedar board and batten. There are a few houses in my neighborhood which are T-1-11, one of which is a 5,400 sf house around the corner from ours - what a shame to install T-1-11 on houses like that.
Of course, most also have FPE panels in them too ...
(At least there is no aluminum wiring.)
That's an indication of 'Good builders gone bad' ...
