They didn't really have a chameleon. See "Experimental setup" in the linked paper [emphasis mine]:

> After fabrication of the meta-optic, we account for fabrication error by performing a PSF calibration step. This is accomplished by using an optical relay system to image a pinhole illuminated by fiber-coupled LEDs. We then conduct imaging experiments by replacing the pinhole with an OLED monitor. The OLED monitor is used to display images that will be captured by our nano-optic imager.

But shooting a real chameleon is irrelevant to what they're trying to demonstrate here.

At the scales they're working at here ("nano-optics"), there's no travel distance for chromatic distortion to take place within the lens. Therefore, whether they're shooting a 3D scene (a chameleon) or a 2D scene (an OLED monitor showing a picture of a chameleon), the light that makes it through their tiny lens to hit the sensor is going to be the same.

(That's the intuitive explanation, at least; the technical explanation is a bit stranger, as the lens is sub-wavelength – and shaped into structures that act as antennae for specific light frequencies. You might say that all the lens is doing is chromatic distortion — but in a very controlled manner, "funnelling" each frequency of inbound light to a specific part of the sensor, somewhat like a MIMO antenna "funnels" each frequency-band of signal to a specific ADC+DSP. Which amounts to the same thing: this lens doesn't "see" any difference between 3D scenes and 2D images of those scenes.)