Answer: This shrub has a horizontal branching pattern with an overall somewhat rounded outline -- it is naturally wider than tall, in the 8 to 10 foot range, at maturity. The horizontal line is accentuated by the way it holds its blooms so a plant in full bloom will demonstrate the layered look most clearly. (It is also evident in winter when the branches are bare.)
In my experience, the overall impression when out of bloom but in leaf is of a more dense and rounded plant, especially when it is grown in full sun. In shade, the horizontal branching is more evident because the foliage is not as thick and the plant tends to reach wider for more light access.
Also, the horizontal lines become more apparent with age. In the full view photo I believe the plant may have been shaped by a somewhat recent pruning and does not show width in proportion to its height.
In an answer to your question, it depends somewhat on your expectation and somewhat on where it is grown, in sun or partial shade but Michael Dirr's respected "Manual of Woody Landscape Plants" does describe it as "Horizontal, tiered branching, creating a stratified effect, appearing rounded to broad-rounded at maturity."
Q&A Library Searching Tips