I think that you might be close - is often times a parallax issue that many rimfire shooters do not recognize. But if your 10x40 has AO, is about a non-issue for you. My experience with older rimfire scopes was their very minimal eye relief - would cut you up, if used on a rifle with any amount of recoil - but maybe newer ones have similar eye relief to centre fire scopes??
To check any scope for parallax sighting error - regardless if rimfire or centerfire on the label - set up on sandbags or something very stable - sight at aiming point - now move your head/eye side to side or up/down - without the rifle / scope moving at all - and watch if cross hair moves on the aiming spot - if it does, that is parallax sighting error - if it does not move, is not an issue for you at that range. So far as I know, the optics within a scope can be adjusted to be parralax free at only one particular range - likely needs to be re-adjusted for a different distance. So most of the time, we settle for "good enough", but I suspect very precise shooters might want better than that. I have a Leupold Freedom 2-7 rimfire scope - booklet says is set to be parallax free at 60 yards - at 20 (?) yards, by seeing some black on one side, then to some black on other side - I can move those cross hairs about two inches versus the aiming point. I suppose if you grasp and hold the rifle perfectly identically each time, there is no parallax sighting error to deal with.