Trunk comparison: Kia Sportage vs Mazda Mazda CX-60

Key Differences in Brief
The Mazda CX-60 offers slightly more cargo space and a larger opening: with the seats folded down, the trunk is +1.6 in (+2%) longer, and with the first row upright, +3.1 in (+9%) longer.
The height of the trunk opening is +1.2 in (+4%) higher on the Mazda, and the width of the opening is +1.6 in (+4%) larger. The loading edge of the Mazda is +0.8 in (+3%) higher above the road. Depth (loading edge to trunk floor) and the width at the narrowest point are the same for both models.
Highlighting Differences Over 10%
None of the mentioned deviations exceed 10%. Therefore, there are no differences that would need to be specially highlighted according to your criteria (>10%).
Impact on Usability
Practically, the smaller advantages of the CX-60 mean: a bit more space for long luggage, especially when the rear seats are folded down (plus 4 or 3.1 in), and a slightly wider and taller opening, which makes loading and unloading bulky or tall items easier.
The slightly higher loading edge (+0.8 in) can make lifting heavy luggage minimally more difficult. Since depth and narrowest width are identical, the ability to transport particularly wide or low-lying cargo does not change.
Conclusion
The differences in favor of the Mazda CX-60 are present but overall minor and below the 10% threshold.
In everyday use, the practical advantages (easier loading of somewhat longer or taller items) are noticeable but not fundamental: both models offer comparable usability in the trunk; those deciding should consider other criteria such as driving behavior, equipment, or price.