Understanding implicit surface plot behavior

Here is some code that plots an implicit infinite, tilted cylinder.

Q=diag([0,1,1]./3^2);

axis([-5 5 -5 5 -5 5])

h1=fimplicit3(@(x,y,z) quadform(x,y,z,Q) ,'EdgeColor','none','FaceAlpha',0.3);
view([-2,11])
xlabel X, ylabel Y, zlabel Z

T=makehgtform('axisrotate',[0 1 0],pi/4);
h1.Parent=hgtransform('Matrix',T);

My first question is, why doesn't the cylinder, which is infinite, extend to the axis limits?

My second question is, below is the same code again, except at the very end, we double the extent of the axes. Why does the cylinder become invisible when this is done?

figure;
axis([-5 5 -5 5 -5 5])
h2=fimplicit3(@(x,y,z) quadform(x,y,z,Q) ,'EdgeColor','none','FaceAlpha',0.3);
view([-2,11])
xlabel X, ylabel Y, zlabel Z

T=makehgtform('axisrotate',[0 1 0],pi/4);
h2.Parent=hgtransform('Matrix',T);
 
axis([-5 5 -5 5 -5 5]*2) %<----makes the cylinder disappear!

function d=quadform(x,y,z, Q)

    xyz=[x(:).'; y(:).'; z(:).'];

    d=reshape( (sum((Q*xyz).*xyz)-1), size(x));

end