All transistors have Miller capacitance which is from the inverting output to the input. In a differential amp , by adding caps by cross over ( From + out to + in and -out to -in ) from internal differential outputs, it tends to cancel the negative feedback with a lesser positive feedback with non inverting current or negative Miller Effect .
When done right, with very low connection ESR you get extended bandwidth and it remains stable.
You are advised to apply this principle inside a differential output OTA, due to parasitic effects of layout and likely instabilities otherwise neglected.
Do you understand Negative Miller Effect is positive feedback?