We checked the POEA website for Advisories or Memorandums pertaining to Canada bound Filipino workers with an Open Work Permit but we didn't find any. They are not supposed to get an OEC but without an official document to that effect, it's pretty difficult to explain the situation to an immigration officer.
We send an email inquiry on November 23, 2020 and we recently received a reply.
The POEA recently issued this Advisory No. 159 series of 2020 pertaining to Canada Open Work Permit which you may download here.
It doesn't categorically states that Open Work Permit Holders are not required to get an OEC, but this will do. The Advisory stated that Open Work Permit Holders are not processed by POEA, ergo, OEC will not be issued.
You may want to print this Advisory and bring it with you for presentation at the Immigration counter in case you're asked about the OEC.
UPDATE: Here's a news release from POEA specifically stating that they are not issuing OEC for Open Work Permit holders bound to Canada.
