That is true, but in reality nobody is going to mix such a small amount of bitcoins, except if they are testing or using Thormixer service for the first time.
I think that most mixers using the same provider have exactly the same minimum amount of BTC set, only Mixtum is offering free service for 0,001 BTC.
Well, I agree with you, if someone is going to use the mixer then he/she will go for high amount of Bitcoins then going for that minimum amount.
Only those who may check the mixer for reviewing purpose might consider choosing the minimum amount option.
It's good to hear that Mixtum is offering free service for 0.001 Bitcoin as that's something unique I guess, and the ones who want to mix small amount might consider their service.
However, the fees of Thormixer are also similar to most mixers out there and that's why I think the Thormixer users will keep using it instead of considering an alternative mixing service.