I wonder if a radical change in a mom's hairstyle/color evokes similar distress. Perhaps not as much, as our facial appearance wouldn't be altered.

Most of the babies look to be of the age when stranger anxiety kicks in.

...they are of the age where stranger anxiety starts to be a thing.

I used to advise parents that this varied in severity from kids who will just be a tad reserved around someone they don't see regularly to kids who regard mom or dad with suspicion when they come home from work at the end of the day. I would particularly encourage them to tell grandparents who didn't live close enough to visit regularly to allow a baby in the stranger anxiety stage some time to accommodate and not just scoop them up for hugs and kisses the moment they come thru the door.

Who wants to be scooped up for forced hugs and kisses by an unfamiliar person? I dislike seeing parents force kids to hug and kiss relatives when the kid obviously doesn’t want to. Especially little girls with older male relatives.