"We mainly use [language X], but you don't need experience in [language X] for us to consider your application" - this is a totally normal thing I've seen in many job postings.
Stripe is sometimes more explicit about it:
https://stripe.com/jobs/listing/infrastructure-engineer-ruby...
"Our most popular language in the company today is Ruby, and we are building a new Ruby services practice in support of this."
... but that job is also an openly Ruby-centric job.
"We mainly use [language X], but you don't need experience in [language X] for us to consider your application" - this is a totally normal thing I've seen in many job postings.