Yes, I wouldn't deem the kneeling partisan representative of the rest of his pack. Much as I love Mark Copplestone's sculpts, he is not very consistent in the scaling of his figures. Some of the worst offenders in that respect were the ones Mark did some seven or eight years ago when he experienced some eyesight problems which forced him to increase the size of his sculpts (the BoB British infantry in Wolseley helmets are notoriously huge). The scale creep factor is also evident within the Bolshevik range : the earlier Red Army infantrymen are shorter and slimmer than the sailors, for instance.
Back to Tsuba Miniatures, I'd say from the comparison pic they should be quite compatible with the Musketeer and Brigade Game Russians, who are the same size are the original Copplestone Bolsheviks.