The charger orifice has plenty of space for a bare JST header, but the USB LiPo charger linked in the BOM has plastic moulded around the base of the JST header to hold it in place. Enlarging the hole a little with a knife makes it fit nicely, but it would be better if it had printed with enough space in the first place.
The standard JST XH header is 7mm deep, whereas this particular charger only exposes 5.5mm of it, before expanding from 10.0x5.8mm to 12.7x8.2mm, when the hole in the robot is only 11x7.5mm.

The charger orifice has plenty of space for a bare JST header, but the USB LiPo charger linked in the BOM has plastic moulded around the base of the JST header to hold it in place. Enlarging the hole a little with a knife makes it fit nicely, but it would be better if it had printed with enough space in the first place.
The standard JST XH header is 7mm deep, whereas this particular charger only exposes 5.5mm of it, before expanding from 10.0x5.8mm to 12.7x8.2mm, when the hole in the robot is only 11x7.5mm.