I suppose that something like this happens but it isn't common. Thankfully. In fact, providing a simple path to a grade that doesn't involve actual mastery of the subject but just answering some subset of questions about it is likely to be counterproductive with at least a subset of students.
Students are busy and will want to take advantage of any short cuts offered.
I doubt that there is specific research that speaks to this, but I also think that the great bulk of research on learning would speak against the practice. For example, see The Art of Changing the Brain, by Zull.
At the end of the day would you as a professor prefer to take on a student who got a lot of good grades somehow or one who really learned a subject and could apply in in creative ways?
I do know of something like the opposite practice, actually. In fact I once benefited from it. I was taking an undergraduate physics course and crammed for the first exam, staying up all night. I failed it. The next exam I got a D, the next I got a C, then a B. I got an A on the final exam. The professor was viewed a something of a hard case, but he gave me an A for the course. I learned how to learn and I improved. But there was noting in the syllabus that suggested that I would be graded that way. And I doubt that any strategy other than steady improvement would have resulted in that outcome.
Similarly, I occasionally let students avoid the final exam altogether provided that they had proven throughout the course that the A grade was appropriate for them. Some other professors would grade the final so that you could only improve your grade there, which is a bit less radical.
If you make grading into a game, a fraction, possibly large, will treat it as a game to their detriment. Stress long term learning via reinforcement and feedback, not high risk exams. Yes, they will avoid other work and think they can "get away with it." Don't encourage such behavior.
However, there is a method of grading that might be a bit similar in structure to what you suggest: cumulative grading.
In cumulative grading every graded student activity has a number of points assigned and the points of all such activities add up to some number, say 1000. On each activity you earn a number of points toward the total. Publish in advance what number of points are required for each grade, say, 900 for an A. Then the student always knows where they are in the course and what grade they have earned. They also know what effort is required in the remaining part of the course to achieve the grade they feel they need.
Students can game this system, of course, working until they have earned, say, a B, and then putting in no further effort.
If you combine this with permission to repeat old work for some additional points then you will encourage people to get the reinforcement they may need. You also don't get complaints about your grading.