The /ɔɪ/ diphthong is spelled <oi> and <oy>. The /ʊə/ diphthong is spelled <ure>, <oor> or <our>.
This is a contrast between two diphthongs with different starting positions and direction of movement. It is not a problem for learners.
Interesting pairs include:
The density figure is 1.4%. The set makes 6 semantic contrasts giving a loading of 54%.
alloy allure alloyed allured alloys allures boy boor boys boors buoy boor buoys boors doily dourly toy tour toyed toured toys tours
John Higgins, Shaftesbury, December 2009