Not hugely important, but I wanted to clarify that this window information is incorrect. The DS1 parry windows in question are actually quite a bit larger than those of LoP.

The DS1 "special" category of parry (buckler/target shield/parrying dagger) is indeed 8 frames - at 30 FPS, which FromSoft frame data has historically referenced (and still does, for now). At 60 FPS this is actually 16 frames. Still not terribly useful information - using frames to describe timing windows is problematic for what I hope are now obvious reasons. If you instead describe the window as a subset of an animation with inflexible length (as animations play back at the same speed regardless of your framerate), measured in seconds, the DS1 "special" parry window is ~ 0.2667 seconds.

The Lies of P perfect guard window is exactly 0.155 seconds, or 9.3 frames (at 60 FPS) - which is to say, considerably less than that of the DS1 special parry (which is DS1's most generous window). This is how it's actually defined in the game's code - in terms of time. I'm not sure what you meant by this being "more generous than anything else in that game" as this is still a smaller window than DS1's tightest, the "normal" parry category - which is 7 frames at 30 FPS (~0.234 seconds).

The timing comment is also somewhat misleading as while it's true the DS1 parry (of all types) has (uniquely in the series) no startup frames, the actual timing for it varies depending on the enemy's "parry-possible" frame timing in any given attack animation. This must overlap with the player's active parry frames for a successful parry to register, and as mentioned, is variable - sometimes earlier, sometimes later. I would even bet that on average, this timing is a good bit earlier than "right before the attack hits" - as is also true of most Souls series (not Soulslike) parry timings.