"not refunding points below 100 seems to create a problem"
Yes. The point is for whom it creates problems.
1. Normal users usually get quite above 100 in a few months.
2. Normal users usually choose wisely their games and never go CD.
3. In the rare case a normal user goes CD, it happens once or twice, not five times like you did (and maybe he already got 400
).
So. Since Points are NEVER refunded when you lose, unless you got less than 100
AND you didn't CD, I can't see any problem created except for those who belong to none of the categories listed above. The solution is pretty simple: try and do your best to get into one of them. Personally I suggest you to get into category #2. And if you're "just curious of the policy"... well... the policy is just suggesting to you the same.