Stashaway recently updated their terms "we may net the buy orders against the sell orders before placing your orders in the markets." What does this mean for us? Pros and cons?

Take a scenario, A wants to buy $500 and B wants to sell (withdraw) $100. StashAway can simply transfer A's money to B and buy into the respective securities with the remaining $400.

The $100 for B which is still currently invested can be transferred over to A's name. There is no difference for customers, but it can help save transaction costs for the company when such transactions happen very frequently.