Giga means 1 billion and not 1 073 741 824.

No. Not when you are referring to computer equipment, memory capactiy, and storage capacity. Terms like kilobyte, kilobit, gigabyte, gigabit, megabyte, etc., because they specifically refer to bits and bytes, should adhere to the powers-of-two rule.

Therefore, when someone says "gigabyte", it should always, in all cases, mean 1,073,741,824 bytes. Anyone who means "a billion bytes" is either being deliberately misleading (as is the case with drive manufacturers), or is simply mistaken.

If someone said "gigameter" to me, or "giga-acre", or "giga-mile", then I would expect it to be in powers of ten. But because you used the word byte as part of your statement, I expect it to follw the rules of bits and bytes, which is powers of two.