A seat can be secure at 55% just as it can be at 95%. Packing and cracking both tend to yield secure seats - if nobody could confidently predict who would win the seats, how would it be gerrymandering?

The first one is.

no, it is making your opponent's seat more secure.

Think about it for more than half a second.

Moving a Democrat into a Democratic district makes that district's Democratic seat more secure.

At the same time, moving that Democrat out of your district makes your Republican seat more secure.

You can't do one without the other.

Probability of victory is highly non-linear in the proportion of voters. It's so non-linear that it makes sense to treat it as a phase transition. A district is secure when the outcome is certain. There are two distinct phases where the outcome is "secure" and the border between these two phases is, because of the non-linearity, very small. That is what secure means to most people.

The specific language that the OC, and almost all journalism uses to describe the strategy is "making districts more secure". The only way to interpret that, in the context of the phase definition of security, is adding voter proportion to a district which is already secure. This is never in the interest of the party that it is happening to, so yes, it is dishonest to describe it this way.

As I just pointed out to you, it can never happen to one party without simultaneously happening to the other party. Packing Democrats into an already-secure Democratic district adds Democratic voter proportion to their district and adds Republican voter proportion to yours.

If you don't believe that this can be in the interest of either party (since it's happening "to" both of them), you don't have much left to complain about.