If you knew a little bit about how macrovision worked, you'd be able to reason why your "fun fact" doesn't make logical sense. So let me give you some details
1) Most VCRs (I'm not sure if this was always the case or only in later years) contain an automatic gain control in the recording mechanism. The AGC would try to adjust the picture brightness based on the signal it received, so that what you recorded would be neither too dark nor too bright. I'm not familiar with the exact mechanisms they use to calculate how much adjustment to apply. Many VCRs also apply this AGC processing to signals that are merely passing through the VCR, even if you aren't recording
2) As an unrelated fact, analog video signals actually include the closed captioning data encoded into the video feed. This data is encoded into a part of the video stream that usually isn't displayed on your TV. However, sometimes you may see this data when playing back the analog signal on a digital display, if overscanning is turned off. If you've ever seen video with a row of black and white dots/bars at the top, that's the closed captioning data.
3) Along comes Macrovision. Some assholes discovered that if you manipulate the signal contained in the closed captioning data, you can often screw with the AGC mechanism in VCRs, causing it to repeatedly alter the video signal from brighter to darker. Also, because VCRs often apply this AGC to signals being passed through, this also explains why you usually couldn't hook up your DVD player to your VCR to get around the fact that your older TV didn't have RCA inputs.
So if you think about this, there is no reason why it should matter if the VCRs are the same brand. With any VCR, the signal it outputs is going to be the same, no matter whether hooked up to a TV, a VCR of the same brand, or of a different brand. Likewise, the input signal is going to be processed the same, no matter whether coming from a VCR of the same brand or different brand, a DVD player, a camcorder, or a cable box. The only thing that makes the difference is the implementation of AGC in the VCR. Either
A) Your VCR implements AGC in a manner that is susceptible to macrovision manipulation
B) Your VCR implements AGC in a manner that ignores this extra data.
C) Your VCR doesn't do AGC
If the VCR doing the recording falls into category A, then it won't work right. If the VCR falls into category B or C, then the macrovision won't have any effect on you. I think Occam would say that the simplest explanation would be that the VCRs you worked with fall into category B or C.