Simply look at the rules quoted in the post before yours.
If the player simply places 8000 chips towards the pot, it is crystal clear that his raise is to 8000. Same if he places 10,000 chips towards the pot -- his raise of 8000 over the previous 2000 (10,000 total) is crystal clear, and he has said nothing
But if the player announces "Raise, eight thousand", then the total bet is 8000 ~unless~ muddied by additional verbage or physical action -- which means things AREN'T exactly crystal clear. If he tosses out 10,000 chips while making that declaration, it's a raise of 8000 over the 2000 to a total of 10,000. Same if he adds "more" to his statement. But if pausing between his verbal and physical actions (and someone please define 'pause' for the record, please), then his verbal is binding regardless of what he does physically.
So by speaking, he adds a variety of opportunities to be misunderstood -- while simply making the physical bet he wants with no unnecessary verbage there is NEVER a misunderstanding of the bet amount.... because chips speak, for good reasons. And as alluded to earlier, verbals often just muddy the water, while the intent of a simple and silent physical action is crystal clear.