[HELP] Film grain appears to be reduced despite not attemping to remove grain or denoise

[PJWong]

(I'm new to this space, so please be patient with me!)

I'm digitizing VHS tapes for the first time and am using Hybrid for the sole purpose of deinterlacing, adjusting the pixel aspect ratio, resizing, and changing the color matrix.  I'm not looking into "restoring" these tapes, at least for now, so I'm not interested in any de-noising, de-graining, sharpening, etc. and do not touch any of those filters in Hybrid.  I'm simply looking to digitize some tapes, do the minimum amount of post-processing, and then upload to YouTube (hence the resizing/color matrix step, as YouTube has awful bitrate for SD content).

However, after processing one of the tapes, it appears there's less film grain/noise than before.  It's not a huge difference, but I took some screenshots to compare side-to-side (left is the original avi and right is post-processed).  There seems to be a noticeable reduction in grain and noise, which I can live with, but I also wanted to make sure I wasn't applying any kind of denoise/degrain filter by accident.  I know the comparison pictures aren't frame perfect, but I think they're close enough to get the idea:




I don't know how to share my profile, but below are screenshots highlighting the only major changes I made from the Hybrid defaults:







Any reason why there appears to be less noise/film grain in the post-processed video when compared to the original?  Any setting I may have overlooked, or incorrectly adjusted?  Or is this just the natural consequence of using QTGMC to deinterlace?  Or of using bicubic spline to resize?  Any insight would be greatly appreciated!