There’s always more than meets the eye. When adding a stock you have to take into account everything that’s involved in the process. Corporate actions, logos, search bar industry/sector categorization, compliance checks, data feed checks, etc…
Also, depends on the instrument. US stocks are generally the quickest, due to configurations being slightly simpler. While ETFs, for example, are the most time-consuming.
P.S. The goal of 10,000 securities by year-end is still on the table.