The only way there is a "hole" in the language is if a driver with less than four years doesn't do his due diligence the beginning of each week and try to get himself "assigned" to a route, if he is intent on opting into 9.5 protections. First, he/she should go up to the dispatcher and find out what they are to be doing that week; again, if the PLAN is for them to be assigned to one route, then they have 9.5 protection right there, nothing ambiguous about it. If the dispatch supe, oncar supe, or center manager tells them they will be on such-and-such this WEEK it is a done deal. The only worry one would have is if the management person in question would blatantly lie and say they never said anything like that, opening up a he said-she said debate; how that is won, I don't know.
Now, if upon asking mgmt what the assignment for the week will be the answer is, "Well, not sure. Bobby has off today and tomorrow, so I'll put you on him. Tiffany has off Friday, and I think Jim has off Thur-......", well that driver isn't being ASSIGNED a route, therefore they are not covered by 9.5 protections. However, if it were me, and I really wanted to qualify for protections I'd be asking around, seeing if I can't get a cover who due to years of service qualifies for the list-or just doesn't care-and maybe has an assigned route locked down. I'd see if he'd mind doing what I'll be doing, and if he agrees getting the approval of mgmt, although a reason other than "Trying to make sure I can qualify for the 9.5. list" will need to be given. This scenario would only be feasible if the low-seniority guy knows the route in question, and if the cover driver has good knowledge of the center's routes.
The point of all this is new guys should be encouraged to be proactive and aggressive in pursuing what they would like, which is "an assigned route" or management agreeing to assign them to ONE route for that week, on Monday. Once they have that they are protected. The stewards and other knowledgeable employees should educate the newer or less-experienced drivers about their rights, tell them what to look for and how they can get it. However, the language as it stands is not weak; drivers must make sure their efforts to be protected by them aren't weak.