If you hate it when nouns are used as verbs, it's time to consider that the words that and up can be many different parts of speech.
Some Verbs Can Be Both Helping Verbs and Main Verbs
That is not the only word that does double (or triple or quadruple) duty. The words have, be, and do, for example can be auxiliary verbs (you may know these as "helping" verbs because they "help the main verb") or the main verbs themselves. In “I have just arrived,” the word have helps the main verb (arrived), but in “I have a question,” it is the main verb.
‘Up’ Can Be Many Parts of Speech
Sometimes words are so common that we don’t even think to question their status. Take the word up. It’s a preposition, right? "I walked up the block for a cup of coffee." But up can also be an adverb as in "He jumped up." Or it can be part of a compound verb "We fixed up the house" or "She wrote up the report." Up can even be used as an adjective or verb: "It was an up day for the markets" or "The university has upped tuition again." The stereotypical characterization of up as a preposition doesn’t do justice to its flexibility.
English Words Are Often Flexible
The flexibility and homonymy of English words is pervasive: words like yesterday, today, and tomorrow can be nouns or adverbs. Compare "Tomorrow is another day" with "I’ll finish the work tomorrow." The word who can be an interrogative pronoun (“Who left?”) or a relative one (“I saw the person who you mentioned”). Before and after can be prepositions or subordinating conjunctions: "I left after class" or "I left after I saw them." Well can be an interjection or an adverb, as in "Well, I never would have believed that!" and "The old car runs well." And of course, you and they can be singular or plural pronouns.
So if you expect a word to have a unique meaning or function, you are likely to be disappointed. Words are pressed into service for new functions all the time and the list of such grammatical doubles goes on and on.
Sometimes, though, the status of a word becomes a matter of minor controversy. A librarian I know was called out on social media for using fun as an adjective (a fun event). "As a librarian, you should know better," her on-line scolder remarked. Well, fun has been an adjective for quite some time. Others get annoyed about the shift of super from adjective status to intensifying adverb (as in “She was super smart”).