Your phrase "competitive as possible" is wrong or at best very misleading. If a district intended to be a "bare win" actually turns out to be competitive then the restricting process has gone wrong from the point of view of the controlling party.
The goal of gerrymandering, often achieved in practice, is to disenfranchise as many voters of the other parties as possible -- to ensure that their vote has no effect on the outcome of the election. So the first statement you quote is accurate.
The second statement you quote just explains how this can be done.
Packing all the democrats into a single district could be described this way; most of the votes in such a district will be wasted democratic votes. But that opening statement was
> [Gerrymandering] creates districts that are skewed and uncompetitive, denying voters the ability to elect representatives who fairly reflect their views.
(my emphasis)
This can't describe the phenomenon the article is actually about. It's about segregating people such that they can easily elect a representative who caters to them. And in fact this kind of redistricting is often legally mandated, specifically so as to give minority voters an uncontested district from which they can elect a minority congressman.
Enemy party concentration can give the boundary-drawing party extra representatives counted at the state level compared to expectation. But it obviously reduces the number of enemy-party voters who suffer from being unable to elect their own representative. The skewed districts created by gerrymandering make it easy for voters to elect a representative who reflects their views; the close districts make it more difficult.
> PARTISAN gerrymandering is an offense to democracy. It creates districts that are skewed and uncompetitive, denying voters the ability to elect representatives who fairly reflect their views.
But the issue they're talking about is actually the opposite of this! Further down:
> Partisan redistricters stuff voters of the opposing party into a smaller number of districts, while spreading their own voters over a larger number of districts to eke out as many bare wins as possible. It is possible for a party to win more than half of the popular vote in a state, yet control fewer than one-third of the legislative seats. This is not a theoretical problem: Precisely such a thing happened in 2012 with the congressional delegations of Pennsylvania and North Carolina.
The charge here is that the party controlling districting wants to make it as easy as possible for voters in the enemy party to elect the representative of their choice, by taking away all of their opposition. At the same time, the controlling party is trying to make the districts it wins as competitive as possible (while staying above 50%). Any votes you earn above the 50% threshold would be put to better use in some other district.
Now, the strategical analysis is perfectly sound and this is a reasonable complaint to make. I just think it's funny that the rhetoric of the piece is actually opposed to the policy complaints.