You are going to have to provide authoritative citations to convince me. Until then, the plain English meaning of the phrase, which is repeated in the instructions, shall prevail in my understanding.
OK, here we go. Section 5(1) of the Citizenship Act, most recently modified by bill C-6, sections 1(1) 1(2) 1(2) 1(3) 1(4), coming into force on Oct 11th reads as follows:
5 (1) The Minister shall grant citizenship to any person who
(a) makes application for citizenship;
(b) [Repealed, 2017, c. 14, s. 1]
(c) is a permanent resident within the meaning of subsection 2(1) of the Immigration and Refugee Protection Act, has, subject to the regulations, no unfulfilled conditions under that Act relating to his or her status as a permanent resident and has
(i) been physically present in Canada for at least 1,095 days during the five years immediately before the date of his or her application, and
(ii) [repealed]
(iii) met any applicable requirement under the Income Tax Act to file a return of income in respect of three taxation years that are fully or partially within the five years immediately before the date of his or her application;
[...]
This is where the "you must have been eligible yesterday" comes from. Everyone who files their application today filed it when the Citizenship Act as above has been into force. The old version of the Citizenship Act has no legislative power, apart from legacy applications, according to the transitional provisions of bill C-6.
So the only question, the case worker can ask is: Was the applicant physically present in Canada for 1,095 days on the day before the application. The answer to that question is yes.
Note that according to the legal framework of Canada, Bills passed by parliament supersede any government regulations and guidelines used by government officials. So the law above is the primary source, everything else is subordinate to it.
