That is probably right, I do see more grain with Rodinal than I do with HC-110. But when I use TMY-2 (Tmax400) in 120 it doesn't matter. The two methods I use are 1. TMY-2, at 250, Rodinal 1+50, 12 minutes, 30 seconds initial agitation, 3 inversions per minute, 68 degrees, and 2. the same except 10 minutes Rodinal 1+50 and finish off with 3 minutes in a Twenty Mule Team Borax mix of 5ml TMTB and 500ml water, no agitation just stand; fix, etc normally. The 12 minute method is off the Rodinal sheet.
The above images was with method #2.