serious question

okay according to fuin mastery rules:

Mastery - Now you can write seals using chakra, ink, blood or any other substance, you can make them form even in the middle of the air, or on any other surface, you can seal everything and you can form complex seals in just a single second. You have knowledge of all canon elemental techniques up to the rank of A and all of the canon techniques of your element. At this level, Funjutsu up to Rank B only use one fourth of the typical amount of chakra. Funjutsu of higher ranks, up to S-Rank, cost half the chakra amount required.

and yet this technique is just chakra and is also C rank:

Name: Finger Carving Seal
Rank: C
Type: Fuuinjutsu
Used For: Writing
Element: N/A
Range: Contact
Duration: Permanent
Hand Seals/Charge up: None
Description: The user concentrates chakra into their finger and using the heat from that, can apply writing of whatever they want to a surface. This technique however requires them to be very delicate with their chakra control.
Weakness: This technique causes slight discomfort for a living target and if it is on flesh, it will scar‏

So what is the ruling on that? Can someone without mastery use a C ranked tech or no?

but the question is with mastery is it writing with chakra or writing it onto chakra?