Some "grass-fed" beef probably isn't

I have been buying grass-fed beef for several years now. The reasons were few: health benefits through better Omega-3 content, CLA (conjugated linoleic acid), more vitamins, better treatment of animals. And the game-y, beefy flavor.

The problem is when I bought grass-fed beef from the local California Hearst Ranch and from Trader Joe's (New Zealand grass-fed beef), the beef had visibly little fat marbling and had that distinctive gamy (wild game-like) flavor, but when I bought so-called grass-fed beef at some other retailers, the flavor was the same as the regular, corn/whatever-junk-they-can-find-fed beef. In some cases, there also was suspiciously too much fat in the meat.

Examples:

• Costco used to sell packs of grass-fed organic beef sourced from Uruguay. The beef didn't taste grass-fed, was tough and chewey.
• So-called grass-fed beef bought at Ralphs had a lot of fat streaks and didn't taste grass-fed, despite being allegedly grass-fed, organic and locally raised in California.
• In some other instances, beef called grass-fed didn't taste as such

What does it mean? I will reserve judgement, but I will not buy these products as I trust my tongue and eyes more than I trust the labels. Not sure who, if anyone, checks if the beef claimed to be grass-fed is actually is. I will keep looking for and buying beef that tastes grass-fed.