Who could explain the announcement regarding SegWit support because since there was no difference between a '3' SegWit address and a Multi sig address, both withdrawals and deposits should've worked before or does it mean they will process all withdrawal using SW?
Wow, hard to find this 'announcement'. Nothing to see on
https://www.bitfinex.com/posts. Their Twitter account points to
https://medium.com/bitfinex/bitfinex-adopts-segwit-8e6c5d72fcf9, the information provided does not make much sense.
In the past they used P2SH (3) addresses for deposits and switched to P2PKH (1), guess after the hack 2016? And have now implemented SegWit addresses (P2SH-P2WPKH? starting with 3 again), which is great.
Not sure what "we can provide our customers with bitcoin withdrawal fees that are up to 20 percent lower" means. As far as I can remember they paid transaction fees during the whole BeeCash spam attack, I've never paid any transaction fees for a withdrawal, which is nice.
Using your (new) SegWit address will enable them to save transaction fees/size, which is good. However, they already used batch transactions since... a very long time.
So yes, it looks like they want to use SegWit for batch processing withdrawals and therefore ask us kindly to use a new SegWit address for our deposits (not sure, but as far as I know you need SegWit address inputs for a SewgWit transaction). But this is just my guess, the marketing story does not make much sense.