No magic Cobras, just math on the curve. Come on man.

If you have a pubkey in the 2^255 range, and subtracted a pubkey that on its own is in the 2^128 range, the 2^255 range pubkey would
still be in the 2^255 range because 2^255 is massively larger than 2^128.  It's easier to visualize this in hex format for the private key.

2^255 private key:

3e2e2ae352cf04aa1bd62491af51349b559f52cdbd2140a7a8c072a1fae6ffd5

2^128 private key:

0000000000000000000000000000000038376ad83f26a0bc5e8a8b62e826a267

If you subtract the two, which by the way, this is straight hex math and works, just subtract the two; equals:
3e2e2ae352cf04aa1bd62491af51349b1d67e7f57dfa9feb4a35e73f12c05d6e

But when you shift/divide a public key, then basic math goes away and you have to mod p this and mod p that.

If someone will generate a random private key in the range of (let's keep it small to show it works and can be checked quickly):

8000000000:FFFFFFFFFF

and post the PUBLIC KEY of that random private key, I will shift it down 1 range and also divide it by 2^5 (keep this small so we
only generate 32 public keys to check).

Then if anybody wants to, they can check to see that it works and it's not BS or magic.