There's a Bloodgood 'looking' JM outside where I work that is about 30 feet wide and probably 35 feet tall. The top of the tree comes to the bottoom of the 3rd story window of my building. I don't know for sure what it is, but all its features point towards Bloodgood. It's definitely on the large side of the biggest size estimates.

The straight species Acer palmatum has the ability to get to a pretty large size - 30' trees are not that uncommon in this area and they can get larger - but it takes considerable time to reach those types of proportions. Trees growing in a somewhat restricted area, like an atrium that is enclosed on 3 or more sides, will often produce a growth habit that is determined more by the circumstance than by nature, growing taller with reduced width.

And keep in mind that mature sizes listed in resources represent a typical average - depending on situation, care and longevity, trees can and often do grow taller than the 'maximum' heights listed.

Vertrees book has some of the Acer japonicum maples growing to pretty large sizes like 'Vitifolium'. Not sure about some of the other ones under the species japonicum. Vertrees is a great reference and has a listing/table in the back that has the size for all at maturity.
Justin