Not sure why they're on Pixiv with that tag - the upload gets that from there somehow.
Looks like @BrokenEagle98 added "バレンタイン" to the Other Names list 8 days ago, which is also present for the regular valentine tag. I assume it actually refers to the latter, so I removed it.
@OOZ662, yeah that was my bad. Should've checked to see if there was a more specific name. I didn't really consider it, since I have seen other tags overloaded like that before, such as Hotaru (ホタル) translating to Hotaru from Splatoon and also firefly. Another example is Kachuusha (カチューシャ) translating to Katyusha from Girls und Panzer and also hairband.
Doing a quick look through all of the posts with actual Valentine tanks and then checking the associated Pixiv tags, I can see that they were all consistently tagged with the バレンタイン歩兵戦車 tag, so thanks for updating the wiki with that more specific tag.