Once again I think misinformation is being spread. Growlers are DESIGNED to contain beer. They are therefore designed to hold a reasonable amount of carbonation.
What they are not designed for is force carbing or bottle conditioning levels of carbonation. These types of carbonation tend to have intermittent pressures well above the norm that given off by 2.5 volumes of co2 in solution.
It is not unsafe to fill a growler from a tap and then put a cap on it for transport. If it was there would be no way in hell that breweries would be doing it and risking a business crushing lawsuit.
On Tap: 1. Kelly R. IPA, 2. Roter Hund Hefeweizen, 3. Bud Killer Blonde, 4. Red Dog Pale, 5. Roter Hund Oktoberfest, 6. Pumpkin Ale, 7. McRed's Stout (with new nitro system and stout tap,) Cream Soda, 8. ESB # 3, & 9. Ordinary Bitter.