That's entirely untrue. The vast majority of medical-school associated masters programs offer no linkage (I'm assuming by "linkage" you mean guaranteed acceptance). There are very, very few medical schools that offer guaranteed admission for masters students who meet a requirement (I believe its maybe a handful of osteopathic schools and zero MD schools). There are many that offer a "guaranteed interview" for a certain level of performance, but this means absolutely nothing, and barely gives you a better chance at matriculating. If I had a dollar for everyone I knew who got straight As and a high MCAT in a "guaranteed interview" school, and still didn't get in, I wouldn't need to take out loans.
The schools that offer guaranteed admission are pretty much all SMPs, which means you need to get straight As in a medical school schedule (which is a feat most MEDICAL students can't achieve, much less per-meds who need time to hone their study skills). Linkage is great, but it's a super high-risk, high-reward process, and I'm not one to bet my entire future on black. I STRONGLY suggest MBS/MS programs over SMPs. You won't get linkage, but you will have a better chance of actually getting into medical school.
There are a lot of ways to judge a masters program, but from my experience, the availability of guaranteed admission should really not be a major factor.