no full rating refund: bug?

I played 6 three-check games with a cheater and my rating dropped from 2424 to 2181. After reporting him, I only got a partial rating refund: 150 points instead of 243.

Is this a bug?
Thanks in advance!

Please read lichess.org/faq#rating-refund

From the above link:
“ A refund will never exceed 150 points”