I can only tell you in general, because this encrouches on market makers
turf.
Match blocks, are implimented normally when exceptionally large customers are in the market to hedge. and sometimes to defend against manipulators.
Normal mode of market defence against rioting prices, is via CB oopen market operations.
When Cbs are not invoked and markets are suspected to riot. Then sometimes teir 1 market makers group together to absorb the hit until some autorities show up to police.
If you remember, during one of the hand held sessions way back. I skewed positions against a market manipulation , awaiting change of sector to off load the positions. Was waiting for franfurtt to open, if you remember.
The fucnction of market makers aborbing the block deals to to not allow the transaction impact the market. esp if rioting prices is suspected.
If you trade in excess of 100 mio. the normal mode of trade should be block matched. If you try to manipulate market with size of any thing above 300mio then the lower tiers you hitting will be quoting back to back with teir 1 blocks absorbing the impact of the hit.
1 recent example is in Euro/chf
there is certainly a block group at 1.2
is SNB die defend level. so if you want penetrate that, be prepared meet the market makers there.
But what you posted textor seems retail stuff.
Even tier 3 banks can make 10 mio prices withour bating and eye lash.
maybe they want make corp hits invisible to small fishes?
would be sinister to think they withholding size or liquidity from the anchovies.
regards