Surprised to see that any EK pilot would even consider to fly Vnav of FLTchange during a small change in level/ alt.
Basic Airmanship gentlemen?!
For small altitude changes, less than say 3000', use VS and avoid large thrust changes, large cabin attitude changes, risk of TCAS events, more room to correct Atc reclearances,...
This is taught DAY 1 of line- training ab-initios!