You are right, the vesting details play an important role in trading and investing because sometimes we do not see this factor and make a trade and the next day we see more tokens are dumped into the market and now we are in a downtrend, I did not become a victim of this state but to be honest I never cared about vesting until I came to know about its importance.
Vesting time and releasing time of tokens affects traders and speculators more than investors. Because if speculators and traders don't pay attention on vesting schedule and time of token release, they will buy around a time of token release round and can be affected by a short term dump.
With investors, they have longer vision and plan, and if the project goes well, price of token will increase with time, they will not be infected by vesting. However, the point is investing into altcoins is always high risky..
But this don't have the details of every token, as I faced issue finding the vesting details of like 5 to 7 tokens which I found on the 4th website you have mentioned.
It takes time for them to add new projects to their websites as well as Vesting pages. It is normal if they miss some new projects.
You have to use multiple sites to double checks and those third-party sites are only supplementary for your quick research. After first steps with third-party websites, you have to go to a project website to double check their token vesting information.