There may not be exceptions to every rule, but there are a few exceptions to the rule that winter is the best time for pruning. It is generally true that most plants are the most dormant through the coolest part of winter. It is also true that while they are the most dormant, most plants are less sensitive to pruning, as well as other horticultural techniques that interfere with their normal function.
However, certain ‘special’ plants get pruned later, either because it is healthier for them, or just because they are allowed to do what they do best in spring before getting deprived of some of what they need to do it with. Some get pruned rather soon after coming out of winter dormancy. Some should probably wait for their new spring growth to mature a bit. It is not as confusing as it sounds.
Evergreen plants that drop much of their older foliage through winter should probably be pruned late in winter or early in spring, essentially at the last minute, just before new foliage develops. If shorn early and deprived of outer foliage that should survive through winter, photinia looks scraggly as it continues to lose much of what had been inner foliage until new foliage develops in spring.
Red twig dogwood and some types of willows that are coppiced or pollarded to maximize production of their colorful twigs should be allowed to show off their colorful bark for as long as possible. Like photinia, they too can be pruned at the last minute, just before vascular activity resumes. However, red twig Japanese maple really should be pruned in winter so it does not bleed afterward.
Flowering cherry, plum, peach, crabapple and quince are grown for prolific but sterile bloom which is diminished by winter pruning. If they need it, they can instead be pruned after bloom, but before too much foliage develops, or after such foliage matures in late spring or early summer. They do not need to be pruned nearly as aggressively as fruiting trees that would otherwise produce too much burdensome fruit. Some may only need to have dead stems pruned out.