I have also tried an answer by Star Strider, here is the code and here is the figure it generates. Looks like the Y-axis certainly has changed, but the plots are not peaking at 1.
figure(1)
h70 = histfit(x70, 10000);
set(h70(2), 'color', 'm')
delete(h70(1))
yt70 = get(gca, 'YTick');
set(gca, 'YTick', yt70, 'YTickLabel', yt70/numel(x70))
hold on
h90 = histfit(x90, 10000);
set(h90(2), 'color', 'y')
delete(h90(1))
yt90 = get(gca, 'YTick');
set(gca, 'YTick', yt90, 'YTickLabel', yt90/numel(x90))
hold on
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