Relatively new parent here. I regret to inform you that your hypothesis is incorrect, at least for my kid. He’s still an infant, though and I don’t know if you include kids under 1 in “small children”.
My wife and I only use our phones to track his nap times, take a picture of him occasionally (once a week or so), and make phone calls. He is still magnetically attracted to them. If you leave one sitting on a surface he can reach he will go for it and start trying to get it to light up on the lock screen. This is especially frustrating for my wife and I as we intend to restrict screen time as much as possible through early childhood.
Even removing social pressures and constructs around phones they are little boxes with moving lights on one side that respond to your touch. That’s inherently interesting to children even before they can meaningfully interpret writing or abstract images.