The 16+16 16145''s were the 40kmh overdrive units. speeds 1-3 had the transfer ratios of 2-4 on a 4 cylinder, the 3rd being direct drive, where the new 4th was an overdrive.
They didnt just simply removed the 1st gear, they took out the 3rd gear and increased the layshaft speed so the gears of gear 1 and 2 would run 30% faster, providing the same output ratio as the original 2nd and 3rd gear, thereby decreasing the maximum torque on them also by 30%. Removing the splitter would reduce the stress by 25% or so, its a possibility to reduce the transmission stress too, but i''ve never seen 161''s other than 12 speed, or 16+16 overdrive.
Ford and Deere use the same trick, Ford in the TW series with overdrive 16+4 dual power, and Deere in the 4040 series quad range. The lightest two, 4030 and 4230 had an underdrive 2 stage powershift and small ratio final reductions. the 4430? and 4630 had an overdrive powershift and high reduction ratio final drives. That means it didnt have more friction than needed to transfer the power of the smaller models, preventing that the smallest models would feel too sluggish (thats the reason Case never put the 80hp Maxxum 5110 prototype into serial production, it was too sluggish, so they started off with a 90hp 5120)