With all due respect, I believe you're wrong in your thinking - here's why :
With USB2.0, on the same laptop computer (ACER 8920), I m used to getting roughly 30Mbytes/Sec both for read & write (big files) on my external USB2.0 WD Passport.
With Transcend 25M3, the USB 2.0 compatibility mode offers me almost 1/3 of that for write operations. Even if USB3.0 mode is a lot faster (I still haven't tested), I would expect to get the maximum transfer possible with USB2.0 operation that most computers have and not a crippled one (~11MB/sec). With one word : USB2.0 operation is crippled - the device is not using the full transfer capabilities of USB2.0.
To be quite fair, its perhaps its because the laptop isn't providing eough power to the USB device - I will test with the extra power cable & I''ll get back to you. But still I think Transcend 25M3 is crippled for USB2.0 operations on my laptop, which is a shame.