Yes - half and half
you more or less answered your own questions. In part it depends on what you are raising. Putting the Osmocote in bags does allow you to remove them for the "clear water flush". And to remove them for "treatments", for example, the 6 to 8 weeks that a JBP is doing its second flush.
if you are raising Japanese black pines, you fertilize heavily in early spring, remove fertilizer a week or two before cutting candles, cut candles roughly 90 to100 days before your average first frost, resume fertilizing after new second flush of candles has mostly hardened off.
Maples, only clear water spring into early summer, then moderate fertilizer rest of summer and autumn. Similar with most deciduous.
Seedlings where rapid development is wanted - moderate to heavy fertilizer year round.
So you see, unlike orchid people, you don't fertilize everything, all the time.
In order to keep internodes short, fertilizer is withheld in spring from many species, if not most species. But fertilizer is put on usually beginning after summer solstice, after the spring growth has slowed and hardened off. And there are many individual exceptions.
