Sorry, not true. You have the name right but the usage wrong. Slotted
nuts are used on truck and automotive spindles, not Castellated nuts.
There is a difference.

I suggest you consult a dictionary for the meaning of castellated,
a hint, it has nothing to do with truck & automotive spindles.

Just for fun, OED says:

----
castellated ('kæst@leItId), ppl. a. [f. med.L. castella¯t-us (see above)
+ -ed. (Earlier than the vb.)]
[...]
c transf. Of a nut or disc: having grooves or recesses on its upper face.

1904 A. B. F. Young Complete Motorist iv. 74 Castellated nuts are
used throughout, with split pins. 1922 Times 20 June 8/5 The wheel and
consequently the castellated shaft will be rotated.
----

My motorcycle has 'em on the ends of the axles.