Yes, it would very well seem that Elizabeth's words were heard by Darcy as an innuendo conveying the idea that there was at least the beginning of an understanding between them. Certain as he was of the very great honour he was doing her, he thought she was expecting, encouraging his attentions. Therefore, he interpreted what she said in this light. This may account for the chair business, which always surprised me, coming from such a reserved character, certainly attentive to decorum (although not as much as his aunt!)

Then Elizabeth's look of surprise is felt as a setback. But of short duration!Could it be that Mr Darcy, though in a much subtler way than Mr Collins, thought she did so only to increase his love by suspense?