"DING DING DING! What do we have for her, Johnny?"
You hit the nail right on the head, mostly. His term began in 1948 or something like that, but his activities did not begin until later. There was no overlap in his activities and HUAAC's activities...
so I have learned... took all of, oh... 15 minutes at a web-capable computer. gee... I wonder why Hollywierdos can't manage the same trick, considering the money they get paid