I have attached a screenshot of the page, where it specifically mentions that it needs to be uploaded.
Also, there have been several cases of application rejection right at the R10 stage, because ECA was not uploaded.
If you err, then always do so on the safe side.
Please upload the copy of your ECA along with your educational credentials, degrees, transcripts/marksheets, and IELTS report.
I am also quoting below a rejection text by IRCC for the very same reason.
"Immigration, Refugees and Citizenship Canada (IRCC), has assessed your application for permanent residence. We have determined that your application does not meet the requirements of a complete application as described in sections 10 and 12.01 of the Immigration and Refugee Protection Regulations. Your application is rejected for being incomplete.
Specifically, your application does not include the following elements:
- Proof of education
You must submit an Education Credential Assessment (ECA) to support your Education documents. Note: A full review of your application was not performed. There may be other elements, not identified above, which may also be missing or incomplete."
and another one,
Immigration, Refugees and Citizenship Canada (IRCC) has reviewed your application for permanent residence. We have determined that your application does not meet the requirements of a complete application as described in sections 10 and 12.01 of the Immigration and Refugee Protection Regulations.
Your application is rejected for being incomplete.
Specifically, your application does not include the following elements:
- Proof of Education
Original copy of your Education Documents (along with the translated version) and an ECA (Educational Credential Assessment) are required.
Note: A full review of your application was not performed. There may be other elements, not identified above, which may also be missing or incomplete.
Refund of fees
As we are rejecting your application, IRCC will refund the fees that you have paid. This includes a refund of the processing fee and the Right of Permanent Residence Fee, if you have already paid this fee.
Job Seeker account Since your application is rejected, you are no longer a candidate for Express Entry and your Express Entry profile number is no longer valid.
If you registered for the Government of Canada’s Job Bank, you should deactivate or remove your Job Seeker profile from the Job Bank website. You should also remove any references that you are a candidate for Express Entry from any private job board websites, if you used any.”