Shipping tags general

Background Pony #3765
Kind of a general question:
I just tagged an upload using the tri-ship tag startrixburst which of course adds several implications. Shortly after, a user tagged each pairwise ship (startrix, starburst, trixburst) which are not implied by the tri-ship tag.
So my question is, are pairwise ship tags supposed to be used in a three-way ship? If so, why wouldn’t they be implied?
Interested in advertising on Derpibooru? Click here for information!
KilianKuro Commissions!

Help fund the $15 daily operational cost of Derpibooru - support us financially!

Syntax quick reference: **bold** *italic* ||hide text|| `code` __underline__ ~~strike~~ ^sup^ %sub%

Detailed syntax guide