"Physical ID" is so not good enough to hit PS4 mechs (and if it were, then Stop Bracelet would work as well), there are several examples of "physical ID" which fail against them, most obviously Alys' Death and Rika's Elim, as well as the enemy skill Cyanic Bomb. There are exactly five PS4 ID attacks which hit mechs:
Brose - magic
Spark - physical skill
Crash - physical skill
Negatis - magical skill
Explode - magical skill
In other words, there is no correlation at all between physical/magical ID and whether it hits PS4 mechs.
Anyway, I've figured out, for myself at least, how to deal with this. Let's look at the five mech-killing ID attacks. Three of them (Explode, Negatis, and Crash) work on damn near everything in the game... literally the only things which immune (or even resist it!) are bosses and two weird ghost enemies. The other two specifically target mechs. As far as I'm concerned, to ID a mech you either need to use an attack which works on almost everything in the game (Tir's spells would qualify... I suppose FE assassin ID would too), or use an ID attack which specifically targets mechs.
Anyway, according to the BoF5 stat topic, Lin's ID is... well, to give you an idea, Meeple didn't even test it! Meeple notes with regard to a different ID move that it is "guessing 50% Success Rate, its hard to find enemies NOT immune". Frankly I think that says it all here.
Lin deserves no respect gutchecks for her ID ever.