You just answered your own Question!
The biggest difference between the two sub groups at A grade to Elite level:-
Racing into shape is a short Peak at full fitness/speed/power etc. Good for a few races and the need for many many races at less elite level.
Those that train to get into shape, then Race to “Fine Tune” = longer season, more predictable performance, less injuries and bigger pay checks! Downside is its a year round plan.
Don’t get confused with doing a L-S plan, if done correctly, Your IN-shape before the season starts, you just need to Fine Tune your speed, SE etc with Racing. An example, is say Asafa, start of season roughly 10.0, then 9.8 to high 9.7’s by end. 0.2 - 0.3 of a sec = fine tuning.
Racing into shape might be running 11sec or even 10.80 now, and 10.40 or maybe the occasional 10.20 by in season with “maybe” a 10.07 or such PB done once.