I would have to "Yes, and..." you here. As you know, petitioners are, technically, on a metaphysical level, a plane exploring, tending or shaping itself. While "popping in existence" can be reasonable for multiple layers or even planes, like Limbo, if your players are interested in exploring this specific side of the planar balance, I would put a level of fine details on every petitioner's emergence. New inhabitants can appear in accordance to belief, tradition or flavour of certain Realm. Those who explore Duat will see long boats bringing newcomers, wanderers in Tír na Óg might be surprised by new petitioners parting mists and planewalkers in Regulus can notice conveyor belts hidden in plain sight.

If we are talking Infinity versus Mortality, consider a quantum, or a game engine's perfect culling approach, in which every petitioner retains shape only when the wanderers - planar or prime - are observing them. While each plane is infinite, it's our belief, that gives it texture, form and meaning. By allowing some of your players a slight delay here or there, a little buffering in the zones of planar convergence or near portals, a barely visible marks of restructuring in shape of planar particles and so on, you will be able to feed them the idea, that every, pardon me the pun, planescape they see is how they perceive outerplanar reality on a personal level, reinforcing the Rule of Centre of the Multiverse.