That was my first reaction too, but on reflection I think the cases are distinguishable. I do say the words "I agree with <Bob>" in meetings, but only when I am acknowledging (and thereby unintentionally endorsing) that there's a difference of opinion. Usually the subject of the difference is already on the table and doesn't need to be spelled out.

By contrast, when I am crediting an idea it's because I had to reintroduce it when it seems to have been dropped; it's not the current subject of discussion. So I say something like "I liked <Bob>'s idea from earlier, to <frobnicate all the bangwoozles with imaginary polarity>".