you are absolutely right, in my opinion the Ferrum project can still be said to be still normal, it's only natural that they postpone mainnet,
I don't know exactly what their reasons are, but certainly if they really activate mainnet it's already a good thing
Ferrum made several changes to their roadmap for a number of different reasons, depending on the target they changed, as for the detailed explanation, you can read this article. hopefully can help you.
https://medium.com/ferrumnetwork/ferrum-network-roadmap-update-21ff56b1ec25