Ann: Further Significant Megabit Success, page-795

I think this would depend on whether the fixes applied in PL4 were driven from HGST or Stanford. Quick read and the announcements after PL3 didn't talk about HGST but definitely talked about Stanford.

if there was no "Joint Development" from HGST on PL4 specifically, I would say this development isn't joint and thus the sharing of information may not fall under that agreement. I.e. 4DS could say "yeah nah".

just because there is a JDA it may not mean HGST has free access to all the info, only on the aspects they have developed jointly...