number of Muslims participating by a couple of the links or they didn't indicate that "thousands" of Muslims participated and "formed a shield." And I note that two of your links are blog posts -- those won't appear in the printed papers unless they're redone as newspaper articles. They're only found online by those who'll look for them.
Here is from the Star Tribune article:
Still, turnout was heavy, as Christians said they were determined to attend. Muslims also joined some services as a show of solidarity, getting permission from church officials ahead of time to get through police limiting access to Christians.
Around two dozen Muslims held a solidarity gathering a street away from the Saints Church — kept back by police. They held signs reading "no to terrorism, yes to citizenship" and "long live the cross and the crescent."
Inside a church in the Cairo suburb of Maadi, several Muslims joined the service, holding candles.
The front pew at a church in the Cairo district of Omraniya was filled with prominent Muslims from the neighborhood.
And this is from the CNN article:
Egyptian Muslims attended Christmas services Friday in a show of solidarity with Coptic Christians days after a bombing killed 23 congregants in the country's north.
Seriously, the above are not the same representation as "thousands formed a shield."
The others did report the "thousands" information. WaPo's was in the form of an Editorial, which will be reprinted in the hard copy of the paper and which, frankly, more people are likely to see if they just scan the site for news.