Disk space has a history of misleading sizing, with 1 "MB" often meaning 1000 KiB, and 1 "GB" seeming to mean any combination of decimal and binary multipliers between 1GB and 1GiB (Including 1000 "MB", which might itself be something between 1 MB and 1 MiB).
Given that mess, I can't see the marketeers taking the trouble to distinguish between total and free space. The first company to honestly advertise the space on their device in the manner you describe will miss out on sales due to poorly written (or poorly understood) comparison tables.
Given that mess, I can't see the marketeers taking the trouble to distinguish between total and free space. The first company to honestly advertise the space on their device in the manner you describe will miss out on sales due to poorly written (or poorly understood) comparison tables.