Potential issue with `findblock[index]` for `BlockUnitRange` with `first != 1`

Perhaps I am misunderstanding how findblock[index] is supposed to work, but this behavior is confusing to me:

julia> using BlockArrays

julia> r = BlockArrays._BlockedUnitRange(2, [4, 6])
2-blocked 5-element BlockedUnitRange{Vector{Int64}}:
 2
 3
 4
 ─
 5
 6

julia> findblock(r, 1)
ERROR: BoundsError: attempt to access 2-blocked 5-element BlockedUnitRange{Vector{Int64}} at index [1]
Stacktrace:
 [1] findblock(b::BlockedUnitRange{Vector{Int64}}, k::Int64)
   @ BlockArrays ~/.julia/packages/BlockArrays/L5yjb/src/blockaxis.jl:299
 [2] top-level scope
   @ REPL[27]:1

julia> findblock(r, 2)
Block(1)

julia> findblock(r, 3)
Block(1)

julia> findblock(r, 4)
Block(1)

julia> findblock(r, 5)
Block(2)

I expected it to return:

julia> findblock(r, 1)
Block(1)

julia> findblock(r, 2)
Block(1)

julia> findblock(r, 3)
Block(1)

julia> findblock(r, 4)
Block(2)

julia> findblock(r, 5)
Block(2)

i.e. in a call to findblock(r, k), I was interpreting k as an index, and thought findblock would output the block that index is in, but it seems to be interpreting k as a value, and is outputting the block that value is in.

Maybe the giveaway is that find* functions in Base find the index of a value, so the current behavior of findblock is consistent with that convention, and really I was just hoping for a different function with a different functionality.

Reproduce the examples with BlockArrays._BlockedUnitRange and inspect findblock in src/blockaxis.jl around line 299. Determine whether the API should distinguish value-based and index-based lookup, then review any nearby tests or documentation before proposing the intended behavior; completion requires an explicit, tested convention or a separate index-based operation.