You seem to be working from the assumption that “warp 10” means ten times the speed of light. This is not the case. In the Star Fleet Technical Manuals, published in the early 1970s, it was explained that speed traveled is proportional to the cube of the warp factor. Warp 5 is 125c, warp 6 is 216c, and warp 10 is 1000c. In the TNG era, they implied played with the formula some more. Voyager had a top speed of warp 9.975, which is now considered to be something like 2000c (which is consistent with Janeway saying it would take 70 years to get home from halfway across the galaxy). Warp factor | Memory Alpha | Fandom But I can’t remember anyone claiming that warp 10 is “merely” 10 times light speed.
My apologies … a day and a half to Alpha Centauri … three days round trip just to find out they have germs …