Framing for synthetic decking usually requires 16” span between stringers.
Some decking such as cedar or Pressure Treated may only require one center stringer on 4’ wide sections.
Pre-molded deck panels often have screw holes in these locations.
Some float drums may require extra blocking for attachment points to the frame if decking requirement does not share the same distance for fasteners. If this portion of the walkway is on legs, the floation blocking will not be necessary.