Some blocks/items do have the translationsÂ
Examples:
crossbow - crosbowz
debug stick - magik stik
loom - paturn addur
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yet for some it just doesn't show
Examples:
stone slab
lectern
diorite slab
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This happens with other languages too, but with slightly different items.
EDIT: shulker shells also don't have translation
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Translations for new items and blocks usually come with the released version (not snapshots). I suggest waiting for 1.14 to be released and then check the translations again.
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PS.
You could help out to translate the game on Crowdin.
(And probably thats where you are supposed to report bad/missing translations)