Something I discovered the other day, while looking for a high-wattage Dell USB C adapter to use with my older XPS 15 (which came with just a old-school charger, so it doesn't get full juice out of most other USB C ones) is that the new 130W Dell USB-C charger only shows up as 90W on an older one like mine.
Looking around, stuff like this isn't uncommon. Apparently a lot of HP's won't work with non-HP USB C chargers at all, for instance.
That's probably because USB c only goes up to 100w for power delivery. Anything higher must be manufacturer specific, so I guess dell hasn't provided any updates for thee older xps to understand the new charger's protocol thing. Not great, but probably not malicious.
I had a xps 15 with 130w charger, and used it with the dell usb-c/thunderbolt docks (wd15/tb16). The wd15 had a 130/180 watt power supply option, after subtracting for the dock's power usage they were specified to provide 90/130w to the laptop. I had the 130 watt wd15 and it still worked perfectly with the laptop. The laptop never discharged while connected (maybe if you spend hours compiling a big project on 8 cores while playing games with the nvidia card?). But I assume it would charge slower/not at all if under heavy load. And the bios warning for a lower power adapter can be disabled.
It should be capable of taking 130w over the USB c port; dell explicitly specifies that it should be used with the 180/240w wd15/tb16 docks which provide 130w to the laptop. XPS 15 9560 iirc.
Looking around, stuff like this isn't uncommon. Apparently a lot of HP's won't work with non-HP USB C chargers at all, for instance.