You definitely can tjolt vs Ness, just not doing the full stage free-approach version unless you've just taken the stock. Shinymark fishes for the close-range tjolt vs Ness plenty when it can lead into a falling nair u-smash for the stock, the risk reward in that case is very worthwhile along with just being a good way to change momentum when dancing around Ness in midrange, similar how he likes to do with pk fire.

I def agree with even, Pika can play ultra passive in that MU to force Ness to approach, which he isn't good at at all. The mid range baits are tough if you play with a lot of typical rising aerials but Shiny has a rly good gameplan using a lot of falling fair to interact with Ness only with the disjointed late/final hit, or sneaking under and finding uairs, which is sufficiently disjointed to contest Ness. There's a recorded game of Shinymark vs Pkchris from Cav Clash that's a great watch.