Who told you that? Maybe correct in his point of view. Listen SEO has different ways to do. Expired web 2.0 has some authority like you will get 20+ PA for sure and if any luck then TF also. This is extra benefit i agreed. But using expired web 2.0 means you will get ranking update its not true. It depends on many things. You can use fresh web 2.0 properties as well and later boost it up with other links. I am using web 2.0 properties for last 6 years and always the new fresh ones. It helps me to update my rank. Here in BHW i have a service for fresh web 2.0 properties. So why people are buying these if it has no value? As i told you study on it. read that guide i mentioned above. It will clear your confusion for sure.
Tips :- If you need to use expired web 2.0 badly you will find lots of service here or fiverr at a cheap price. For $5 you will get 40-50 expired tumblr or blogspot easily. Within $10 using custom deal you can get around 10 tumblr, 10 blogspot, 10 weebly, 10 overblog and 10 wikidot. I bought it once from fiverr.