updating a BSON inside a BSON not working

[DominikZians]

In this snippet, the BSON type is behaving differently than Dict, which seems quite odd to me. Is this behavior intentional?

using Mongoc: BSON

d = Dict()
d["foo"] = Dict()
d["foo"]["bar"] = 42
d
# Dict{Any, Any} with 1 entry:
#   "foo" => Dict{Any, Any}("bar"=>42)

b = BSON()
b["foo"] = BSON()
b["foo"]["bar"] = 42
b
# BSON with 1 entry:
#   "foo" => Dict{String, Any}()

Julia 1.9.3 | Mongoc 0.9.0