The 25% is a hard and fast rule. If the program isn't fully funded, that doesn't mean the coach can offer 10% or 20%. One school my son talked with was funded to 4.8 scholarships, total -- still, the offer must be at least 25% to an incoming student.
Here is the NCAA rule:
15.5.4 Baseball Limitations. There shall be an annual limit of 11.7 on the value of financial aid awards (equivalencies) to counters and an annual limit of 27 on the total number of counters in baseball at each institution.
15.5.4.1 Minimum Equivalency Value. An institution shall provide each counter athletically related and other countable financial aid that is equal to or greater than 25 percent of an equivalency.
15.5.4.1.1 Exception -- Need-Based Athletics Aid Only. In baseball, an institution that awards athletically related financial aid based solely on demonstrated financial need, as determined for all students by the institution's financial aid office using methodologies that conform to federal, state and written institutional guidelines (including institutional financial aid that is considered athletically related financial aid based on the intervention of athletics department staff), is not subject to the 25 percent minimum equivalency value per counter.
15.5.4.1.2 Exception -- Final Year of Eligibility and Not Previously Aided. An institution may provide less than 25 percent of an equivalency to a student-athlete, provided the student-athlete is in the final year of eligibility and has not previously received athletically related financial aid in baseball at any collegiate institution.