The ticklabels are stored as the mantissa and the exponent is stored as the property of the corresponding axis (see below).
So, changing the tick format only changes the values of the mantissa.
Solution - Change the exponent of the y-axis to 0
x = 1:5;
y = [100001 100002 100003 100004 100005];
labels = yticklabels
plot(x, y)
ax = gca;
ax.YAxis.Exponent = 0;
%Check labels after modification
labels = yticklabels
