hiya
i did Montessori training (4yrs ago). will try to cover a couple of things you've asked:
creative/imaginative play- is not actually frowned upon at all. what MM meant by not encouraging fantasy in under 6yos was that she didn't think they should be fed disney and the like, morning noon and night, as she didn't think they could truly separate reality from fantasy (take everything at face value) and that it was thus confusing for them to be fed loads of, well, bull really .
and the point of not feeding them that stuff, is that that stuff is other peoples imaginations, not the child's own.
she thought, and i agree, that a child is perfectly able to have tons of imaginative play with, say, a a cardboard box, when they use their own imagination, which they are more able to do if you don't crowd their heads with half a ton of other (adult) peoples ideas of what children should like and be interested in.
obviously, you take that as far as you see fit. i tend to agree with her, but i do still read my kids stories with talking animals in etc, which a totally purist Montessori approach wouldn't do, i guess.
tis v rare for anyone to be totally purist about it tho,. and in any case, she advocated adapting and changing to follow the times and suit individual cultures etc. what works in basingstoke might need a little tweaking to work in rural Eritrea for eg.
and re the running about- yep, there is def supposed to be space for running about and expending energies, as well as developing gross motor skills.
is, in reality, a v holistic approach to educating a child, on its individual terms at its own pace and following its own interests while nurturing its own personality and self esteem (you know, the real stuff, not just loud and confident seeming facade)
man, i wish there were a good montessori nursery near me