Mac Pro is "Intel" and not desiginated as a "G-series" which were IBM and PowerMac and PowerPC
Apple uses off the shelf Western Digital. Or any other make and brand. There is no "Apple OEM" label or disk drive. You can use any SATA drive or SSD you want. Does. not. matter.
WD Black are fine and most popular probably with 1TB being stock drive sold and used today, and users add and upgrade to other sizes and makes. Including WD 10K VelociRaptors. Samsung SSD (840 currently) and Apple does use Samsung SSD but in that case they have custom Apple firmware for SSDs, but I don't even think they have an Apple logo or label (coudl be wrong, they cost too much for just firmware).
3 years ago, I bought a Mac Pro g5 and was harddrive of Seagate, but it was a sign Apple
But the new device you have purchased a week ago, I did not see as harddrive sign Apple Inc.
Does this mean that he was replaced another harddrive? Or this is normal and happens with Apple Inc
Both drives (Apple-logo and NO Apple-logo) are high-quality drives direct from the manufacturer. The only issue is what warranty coverage would be supplied.
A disk with an Apple logo would be covered under your computer warranty for One year. or if you buy the extra-cost AppleCare, for three years.
A disk with NO apple logo may be covered for three OR five years by the manufacturer. The way to find out is to check the serial number on the manufacturer's web site.
serial numbers on Apple-logo drives will not show up as having a manufacturer warranty. Apple deliberately buys them by the thousands (for much less) WITHOUT warranty coverage from the manufacturer. Then Apple absorbs the cost of warranty coverage themselves.
...But the new device you have purchased a week ago, I did not see as harddrive sign Apple Inc.
Does this mean that he was replaced another harddrive? Or this is normal and happens with Apple Inc...
Since your concern is whether the HD was the one which originally came with your new computer or a replacement, I checked the HD which came installed in my 2010 Mac Pro (I replaced it before it was ever used to have something untouched to put back in case it had to go back to the Apple Store). It is nearly identical to the WD drive in your picture (model, size, labeling, etc.) except that there is an Apple logo in the space to the left of where it says 1.0TB TAH0A. Apple may have changed its policy since my Mac Pro was assembled, but back then they did put their logo on HDs they installed.