I'm not 'on' about anything.
Let me break it down for you:
- Internal transfer rate = rate data moves from platters to the disk controller on the drive
- External transfer rate = SATA2, SATA3 transfer rate = rate data moves from disk controller to host adapter on the motherboard (what we call 'disk controller' despite its moving to the drive)
If internal transfer rate < SATA2 transfer rate, then using SATA3 is moot (with the caveat that transfer rate from the HDD cache may be faster on SATA3 but arguably imperceptible)
If the reader already knew this, the question was rhetorical; if the reader did not know this, it was a relevant question to determine whether performance would actually be degraded using SATA2 vice SATA3.
That's all. No hidden agenda, no conspiracy, not 'on' about anything...