Is This A Bug or Glitch? [Retexture thing]

i just realized i can retexture vanila items by naming the png picture the same png vanilla item,

which then the vanilla texture will then be replaced with the new texture but is this a bug?

For Those who are confused, try this with Mcreator.

1. Download A Picture Of A 16x16 Bone.

2. Name The Picture "bone.png" without Caps Lock

3. Paint The Bone Yellow.

4. Launch Mcreator.

5. Make A Item

6. Import The bone.png and use that picture.

7. Finish Making A Item.

8. Launch A Test Client.

9. Look At The Vanilla Bone And The Newly Added Bone.

10. Done

And To Remove The New Texture, You Have To Remove It In The Resources Tab And Delete The Texture There, Deleting The Item Will Not Work.