pgp7 switch

[MindFuq]

Could someone please tell me what switches are implied by the pgp7
switch?  It doesn't seem to be documented anywhere yet.

What makes me curious is the fact that I can use gpg to create a
ciphertext with these attributes: dsa, idea, z0

PGP 6.5.8 (domestic) has a problem decrypting this.  It accepts my
password and doesn't report a problem; but no plaintext output.  It
just drops the ball.

Then PGP 6.5.1 (international) has no problem with this ciphertext.

When I throw the pgp7 switch, same result: pgp 6.5.8 fails, pgp 6.5.1i
works.

Okay, so pgp 6.5.8 should not work w/ the pgp7 switch, and when I use
the pgp6 or pgp2 switch there is no problem (as expected).  

What I'm trying to figure out is why the older international version
CAN decrypt this; what's the difference?  I thought pgpi was just a
scanned version of pgp, so pgpi should be behind pgp.

(I'd also like to point out that pgp7 should be added to the man
page).