English No. In the classical sense, it is not. An arbitrage is the situation when a player is at least 100% guaranteed against losing the arbitrage, and in most cases a good profit is achieved.
The Polish middles allow the occurrence of a single, though unlikely, result that can reduce the player's bank. You can read more about this in the article about the Polish middles.
Why do we tell about it on our website? This is self-evident: Polish middles are formed according to the same principles as traditional middles, where several events with different outcomes intersect, giving the player the opportunity to earn 5 to 10 times more (on average, there are some deviations) compared to the size of a loss.
This method, though not absolute in terms of reliability, is potentially very lucrative. And if you know how to look for Polish middles (we know it), you can make good money off it.