Does escaping a concealed grappler require a flat check?

Question

Suppose your character is grappled by a creature with the concealed condition. Normally, targeting such a creature with an attack requires a DC 5 flat check.

A creature that you're concealed from must succeed at a DC 5 flat check when targeting you with an attack, spell, or other effect. Area effects aren't subject to this flat check. If the check fails, the attack, spell, or effect doesn't affect you.

The Escape action has the "Attack" trait.

An ability with this trait involves an attack.

If you try to escape the concealed grappler, do you need to succeed the DC 5 flat check first?

Answer 1

Technically yes

Nothing about Concealed restricts its effects when a creature is Grabbed (unlike in P1e). You are "targeting" the grappling creature (from Escape:)

You attempt to escape from being grabbed, immobilized, or restrained. Choose one creature, object, spell effect, hazard, or other impediment imposing any of those conditions on you.

And the [Attack] trait is simply

An ability with this trait involves an attack. For each attack you make beyond the first on your turn, you take a multiple attack penalty.

So the letter of the rules is that this is accurate.

However

Pathfinder 2e is pretty explicit that GM's should lean on ruling in line with what makes sense. For instance, related to grappling, an example ruling is that you can target a creature anywhere their limb is while grappling, even if their "hit box" is not within reach.

Sometimes part of a creature extends beyond its space, such as if a giant octopus is grabbing you with its tentacles. In that case, the GM will usually allow attacking the extended portion, even if you can’t reach the main creature.

With this in mind, it is up to the table whether to apply this ruling or to allow a special case ignoring of Concealed's normal effect. It may even be case-by-case. A humanoid grappling you with one hand might be easier to ignore Concealed than an octopus who has multiple tentacles free to try to cling to you.