Odd minor grid behavior

Hi all:

I recently tried to use minor grids to set up lines around cells in a scaled color image, and have not been able to get it to work, I'm getting lines on the major ticks too. Here's an example:

t=rand(10);
figure
imagesc(t)
xl=xlim;
ax=gca;
ax.YAxis.MinorTickValues=[xl(1)+1:1:xl(2)-1];
ax.XAxis.MinorTickValues=[xl(1)+1:1:xl(2)-1];
set(ax,'yminorgrid','on','xminorgrid','on','minorgridlinestyle','-')

...that gives me a plot like this:

I've tried toggling the major grid with 'grid', setting the major grid linestyle to 'none', neither will get rid of the lines on the major ticks.

The same behavior occurs with a simple plot:

t=rand(10,2);
figure
plot(t(:,1),t(:,2),'k.')
ax=gca;
ax.XLim=[0 1]; ax.YLim=[0 1];
ax.YAxis.MinorTickValues=[0.05:0.1:0.95];
ax.XAxis.MinorTickValues=[0.05:0.1:0.95];
set(ax,'yminorgrid','on','xminorgrid','on','minorgridlinestyle','-')

produces this:

Is there something I'm not understanding about the minor grid behavior? Is there a way to have just the minor grid showing? I've verified this occurs in R2017b and R2019a.

I have a workaround using a for loop to draw lines, but I'm curious to know why this is happening.