Writing a letter claiming language proficiency does not work anymore, unfortunately they will calculate your point without languages and issue a rejection latter. You can search old topic in this forum for assurance.
Accroding to OP 6 Federal Skilled Workers (Operation Manual) that applicants must submit everything in a single package.
"Applicants are required to submit their complete application and other forms, together with all
supporting documents to a visa office within a deadline set out in the notification they receive from
the CIO. This notification specifies that applicants must submit everything in a single package. It
also informs the applicant that the visa office will complete the final determination of eligibility on
the basis of the information on file once the deadline has elapsed. Visa offices are not required to
remind applicants of this deadline."
however; if you keep Reading the manual you'll see this note:
"Note: Any documents received and added to the file prior to the date of the letter, regardless of whether
or not the 120 days have elapsed, must be considered. Visa offices cannot refuse to consider
submissions made after 120 days, if the letters in either Appendix D or E have not been sent. It is
therefore important to produce the BF reports, make the final determination of eligibility and send the
letters promptly."
wish you the best.