His opinion is still nothing more than speculation.
This problem belongs to the domain of experts.
Her piano skill has reached the level of a master.
域 is another suffix meaning 'zone' or 'region' (e.g. 領域), but 圏 more strongly implies a sphere of influence, reach, or classification rather than a plain area.
area; region; district; locality
territory; domain · field; area; sphere; realm · domain; region
area; zone; district; section
sea area; waters
the whole area; the entire region; all parts (of) · the whole field (of study); every field; the whole gamut
wide area; broad region · wide view; zoomed-out view
sacred precincts; sanctuary; holy ground · off-limits issue; taboo topic; no-go area
band; zone; range · bandwidth
drainage basin; river basin; watershed
The kanji 域 originally means 'boundary' or 'region'. The reading いき is the on'yomi (Sino-Japanese reading).
waters; water area
range; register; compass
airspace
within the area; inside the region
regional revitalization; local revitalization
municipal area; city limits; city territory
Shinto shrine precincts · holy precincts; sanctuary
outside the area; outside the zone; out of bounds
scope of work; area of responsibility; range of duties · workplace; place of work
broadband; wideband
vocal range; range of voice; register
western regions of China
theater of war; war area; battlefield
range (of a function)
entering a zone; entry into an area
yen bloc; yen area
leaving an area; exiting a zone
market; business field; commercial sphere
sphere; domain; area
boundary; border; precinct; grounds
cemetery area; burial ground