Higher valuation means MS have to give out less shares now for this acquisition. Although, it’s a complicated topic.
Trying to address your comment - MS makes money with stock market movement but not right away. Higher stock value means higher valuation. If MS decides to raise money by selling stocks then obviously they will get the higher dollar value at that time. Although, it will be painful for stock buyback program.
If you think - my understanding is wrong then please educate me