Not true! Sizes are an iffy thing from 1e to 2e, as follows...
Dragons:
The flat sizes of 1e became the "base sizes" of 2e; however, 2e basically decided that the "base size" would be the 1e size minus the tail of a juvenile (4th age category out of 12) dragon. 1e had 10 age categories (or was that 8?), and vaguely noted that dragons would be bigger or smaller based on age, but was not more exact than that. So, 2e is ONE approximation/specification of 1e's stated sizes, but as 2e also made dragons more powerful in general (well, I guess it is hard to rate, but I think so), I would say that both power and size increased in 2e.
Giants:
Giants were given a size enhancement in 2e as well, directly changing their size values (I think I put up a table in my giants page). I do think that giants were a bit small in 1e (hill giants weren't much different from ogres); bigger giants always make a bigger impression, I say
So, at this point, actually, all of my dragon/giant icons (and manikus' icons, as he followed my table) would match with 2e, not 1e (well, again, the dragons thing is hard to say).
One dragon interpretation of the 1e sizes would of course be to simply use the base size as the whole length of the dragon... which would make them significantly smaller. If we decided to use this interpretation, we could of course use our bigger dragon icons as very old or ancient dragons (from 1e), for example...