I remember when my MacBook pro 2015 started glitching and Apple voided the warranty by saying there was liquid spillage/fluid damage.
So apparently macbooks have these small stickers inside them which change color upon contact with liquids to help detect liquid damage but the issue with those stickers are that they also change color if you live in a humid area.
They made me pay for that repair even though the customer support guy at the store agreed that the color could change because of humidity but it was company policy to charge for those repairs.