4.3.61/ 2d GridGraph/fps drop on open areas related to BFS

i did little stress test for 250 units and found that
when destination near obstacles there no even bfs in profiler/ but on open areas it is fps drop related to bfs
is it kinda planned?)) images from PC/ but i was surprised how lowbudget mobile device handle 400 units. but fps drop on open areas kinda from 25 fps to 8
unity 2021.3.14

how i search pathes - i have parent for agents and on click i loop for each child -SearchPath
agents never recalculate path -only on click