In OpenSSL 1.1.0 and below if you passed a pattern to SSL_CTX_set_cipher_list that didn't match any ciphers the function would return 0 and not set any cipher suites. As of 1.1.1 the TLS 1.3 ciphers are added unconditionally

#include <openssl/ssl.h>
#include <assert.h>


int main(void) {
    int res;
    SSL_CTX *ctx = SSL_CTX_new(TLS_method());
    res = SSL_CTX_set_cipher_list(ctx, "nonsense");
    STACK_OF(SSL_CIPHER) *sk_ciphers = SSL_CTX_get_ciphers(ctx);
    assert(sk_SSL_CIPHER_num(sk_ciphers) == 0);
    return 0;
}

Additionally, even passing the deprecated TLSv1_2_method to constrain the connection to 1.2 will add the ciphers.

The TLS 1.3 suites being added while ignoring the filter was presumably done to prevent situations where custom cipher suite specification would prevent the use of TLS 1.3, but the intermingling of TLS 1.3 and previous cipher suites here where the documented filter is not always applied is more than a little confusing.