Hi Aiden
470?? Wow! As you say unrealistic, but a controller would never assign that. Just like you would not climb a B737 to FL510. Both, 470kts and FL510 are technically possible, hence they are coded into LC.
Without knowing the exact traffic situation, something must have gone wrong there obviously. Most likely in the vectoring somewhere? The general practice is that you use vectors to create the separation between aircraft and use speed control to maintain it.
Also, the speed limit below FL100 is 250kts. I know controllers sometimes waive it, but mainly for departures. Besides, airlines don’t want their pilots to fly fast, as that costs fuel, and they want to use less of it!
Cheers, C