Can a text omission from a provisional application be considered as a new subject matter when submitted for amendment during the chapter 2 of the PCT application?
Not as a matter of right. It is universal that no "new matter" can be added to an application after the filing date. Various jurisdictions take that prohibition more strictly or less strictly. The PCT process leads to entering the national stage in one or more countries. It is those countries, individually, who will decide what is or is not "new matter" or "going beyond". Technically, you can amend the PCT description however you like as it transitions into each country.
Article 28 Amendment of the Claims, the Description, and the Drawings, Before Designated Offices (1) The applicant shall be given the opportunity to amend the claims, the description, and the drawings, before each designated Office within the prescribed time limit. No designated Office shall grant a patent, or refuse the grant of a patent, before such time limit has expired except with the express consent of the applicant.
(2) The amendments shall not go beyond the disclosure in the international application as filed unless the national law of the designated State permits them to go beyond the said disclosure.
In practice, most countries are very sensitive to any added text or drawings, other than translations, so the rule of thumb is that you do not attempt to change the description after filing. However, you can make changes in the description of a PCT application to correct an obvious error. To qualify, it must be obvious that it is an error and it must be obvious how to correct it.
A special case - in the U.S. one can include a previous patent document by reference. That is not the case in most other places. If you stated in the origin al filing that the provisional was included by reference, then you could amend-in text and drawings from the provisional in a US national stage application that flows from the PCT. That is probably not the case you are worried about.