First of all, there appears to be a bug in Inkscape 1.0 which causes the pattern to be much larger than the one created. Hopefully they'll fix it in the next release. The bug doesn't exist in 0.92.3 (2405546, 2018-03-11) - I tested it in both versions.
Anyway, here's a workaround
Draw a horizontal line (don't draw it at an angle or the pattern won't work ...
This worked for me: when exporting via File > Export > Export for Screens, under the 'Formats' section click on the gear icon and 'Anti-aliasing' and then from the pull down menu select 'Art Optimized (Supersampling)'.