I have read that by that time Hitchcock was fed up with the Oscars and thought the Thalberg Award was something of a sop to try to make up for all the times he was passed over. He had considered not showing up, but decided that was going too far.
That’s quite amusing and I have no clue why he did that. Actually I remember some other lifetime award that he received which IIRC had a pretty elaborate ceremony which featured Ingrid Bergman among others. At the end of it Hitch gave a witty speech in his usual deadpan manner.
In fact just now I found the speechon Youtube. It’s terrific.