Why Page Strength on major directories dropped?

I just go through Strongest directories list and checked many directories listed there. Most of them are dropped in page strength by -0.5 and some dropped 1-2. Even dmoz.org which used to have 10 dropped to 8.5. Is this page strength dropped due to decreased of Google Pagerank? I suspicious this because seomoz page strength tools using pagerank as part of their indicator. What do you think guys? Here is another examples.

dir.yahoo.com 10 --> 8.5
business 9 --> 8.5
skaffe 6.5 --> 6
joeant 6.5 --> 6
goguides 7 --> 6.5
2yi.net 7 --> 6.5

 

DMOZ doesn't deserve a 10. Google does, Yahoo does (even though they don't have it), Wikipedia probably does, DMOZ doesn't.

 

you might be true.
Also the PS tool shows different data on different days.

 

ps is not a standard and accuracy.

 

Exactly... nothing more to discuss further about it.

 

Nobody is using PS these days since the tool is unreliable.