I assume it's about the apparently enormous consonant cluster at the ends, which is very rare in English. We have consonant clusters, yes, but not usually with five at once. Although it's actually only three, since "ng" and "th" are one consonant sound each, we just write them with two letters
it's very rare in any language, complexity at the start is not uncommon, but complexity at the end is, also the ordering of the consonant types and the fact there's two fricatives in a row at the end, it's not just a word that not only has no place existing, but also one that should be so unstable it'd change to something less complex in decades at most, yet it's stayed pretty consistent for a while
It's also actually 4 consonants as there's an unwritten k in many accents, or ng is pronounced as ŋg in others, so stɹɛŋ(k|g|∅)θs
the fact there's two fricatives in a row at the end
Isn't that the case for basically any plural noun with a singular form ending in a fricative in English? Paths, months, depths, loaves, dwarves etc. There are also verbs ending with fricatives that do it when in the right tense, like moves, breathes, leaves, or triumphs