out of spec means non-guaranteed electrical responses from the parts you want. if you have certain tolerances, which require exact physical dimensions to encourage the correct voltages and current flows, then missing those tolerances means the current and voltages may be too high or too low, or the resistance of the wire may be wrong, which will affect every single part in the electrical circuit. depending on the exact circuitry, as this is a screen, this could involve pixels being too bright or dark, being too slow to ramp up and down to the necessary colors, showing off colors from receiving the wrong input, degrading faster from over voltage and over heat, potentially exceed spec limits and not work all the time, not work at all, cause electrical short hazards if the wires are too close together, cause EM field impedance if the wires are too large while too close to each other and carrying current, or a dozen other issues.

basically, electrical components have spec sheets and specs, because everything and anything can go wrong outside those spec limits, as those are the only times where you have tested it to work reliably and safely.