it is that the balloting process will be prolonged to the point where the new rule takes over. The blog article suggests that the new rule may itself prolong the balloting process but makes an error when it says it "not unusual" for the 10-12-day point to be reached.
Here's the relevant section of the article you cited (thanks for this interesting piece, by the way):
Despite the comfort of the Santa Marta, the voting is not expected to take weeks. The cardinals say they believe the Holy Spirit is highly involved in the outcome, so anything that smacks of too much politics or too much national or continental wrangling will detract from that. In the 20th century the longest conclave took 14 ballots over five days - the election of Pope Pius XI in 1922. If after three days of voting the electors have not decided on a pope, they will have a day of prayer and informal discussion. A senior cardinal will give them a sermon about their spiritual responsibilities. On the fifth day, balloting will resume.
If, after an additional seven ballots, they still have not elected a pope, there is another pause for a sermon and spiritual reflections, according to the new rules John Paul II made in 1996. After another seven ballots the camerlengo asks the voters for ideas on how to proceed. At this point - approximately 12 days or 30 ballots - John Paul's new rules suggest that the electors will likely decide that to be elected a man need only have a majority of the votes, no longer two-thirds.
So the difference from what the
Americablog article said is in the estimate of how unusual it would be to reach this point:
If after 10 to 12 days of voting a new Pope hasn't been elected (not an unusual amount of time for this process, by the way), then a simple majority of 50% plus one will prevail.
So the statement that it's not unusual to reach 10-12 days of balloting is indeed wrong.
I suppose that the question is: how likely is it that this rule change will reduce the chance of compromise in a strongly divided election in which not quite half the voters are vehemently opposed to the favorite candidate of the remainder? The writer of the blog article is suggesting that it's now possible for a strongly polarizing candidate to be elected because his supporters know that if they hold out long enough, they can trigger the new rule and elect him with just over half the total votes. Under the old rules, once the numbers became clear, plans for a compromise candidate would be made.