In general, no. Most people seem to be using upcut bits that pull router into the material if anything.
However, LR3 isn’t locked down to the table, and does rely on weight/gravity, as well as pull/push force caused by the bit. So, the machine pushing up can happen depending on the combination of machine weight, depth of cut, feed-rate, material density and bit rpm and profile, etc… For example, I have to go slower when using downcut instead of upcut.
For LR3 low, slow feed-rate, with deep cuts, seems to be best way to maximize material removal rate.
My bowflex YZ plate mod helped, but wasn’t the correct fix for my situation… I got the combination/balance wrong and was struggling to get symmetrical V-Bit to fully cut into polycarbonate/acrylic. Adding weight to the YZ plate did help, but using offset V carve bit was a better fix for that task. Am still learning…
Vaguely recall someone in similar situation using MDF stacks to raise their Y rail/rollers. Goal being to have the gantry be as low as possible relative to the YZ plates.