I too kind of noticed this.
But I thought it was due to the amount. As "Monthly expenses" I sent about ~AUD 1000 and it was instant. As "Buying property" it came the following day 12:43pm - but here the amount was higher ~5K.
So I am not sure what exactly caused the delay.
While browsing along I came across this page showing Wise accounts paying out interest for GBP, USD and EUR.
How safe would these investments, since Wise is not a Bank per se.