Personally, would be very difficult for me to reach the "conclusion that H.F. Wichmann most likely knew a Hawaiian silversmith who was trained in the Japanese form of the open-work bon-bon spoon and was the originator of this form"
based on what you've cited and theorized.
Regarding the H.F. Wichman stamped 'Aloha' spoon, seems clear that it is almost certainly by the same designer and manufacturer as the San Francisco and Honolulu spoons - but while it could be earlier, firmly declaring it's a 'decade earlier' based on a sales description stating "c. 1900" is problematic in that 'circa' indicates an approximation since the actual dating is not known.
Concerning a link between Shreve & Co. and Hawaiian souvenir spoons - San Francisco was a port city, with travelers departing and arriving from Hawaii on a regular basis, would be in their interest to have souvenirs available. Shreve & Co. was well known for their works incorporating coins with various origins and dates - in addition to the Hawaiian coin bowl spoon with banana leaf handle, they also produced one with a Mexican coin and a cactus handle.
Japanese silversmiths were very skilled and produced some stunning pieces, including those intended for the Western market (Liberty and Co. advertised and sold a large line of Japanese spoons, late 19th-early 20th century), and they certainly influenced design, but while many Asian spoons have wide bowls in relation to the stem, it is just typical of bon-bon spoons to have wide bowls regardless of their design. Naturalistic spoons were produced long
before bon-bon spoons became popular, and toward the end of the 19th century, well into the 20th, numerous American silver manufacturers were producing examples, including bon-bon and other spoons with blossom-form bowls, as well as holloware - flowers, leaves, branches, vines, seashells, etc, are all attractive elements..
From Snodin's 'English Silver Spoons' (1982, 2nd Ed.), on 19th century naturalistic spoons:
1908 catalog page showing a wide variety of pieces, including a bon-bon spoon, in Paye and Baker's 'Daisy' pattern:
1907 retailer's ad showing Paye & Baker bon-bon spoon in their 'Wild Rose' pattern:
1901 retailer's ad showing Unger Bros. #8026 bon-bon scoop:
1909 retailer's ad showing a Watson flower-form tea strainer, the handle their Floral series No. 2 'Sego-Lily' pattern:
1893 ad for Alvin's multi-motif 'Floralia' pattern: