Do the cabin announcements follow a common protocol?
I can only speak for carriers following FAA regulations. But, It was probably a company policy change. I have a copy of the 2017 FAR/AIM. I don’t remember there being a change since then. 

One reason for an air carrier, whether large or small, to use a standard format and phrases is to make sure that every flight and cabin crew completes all of the required elements of a briefing without forgetting items. In the litigious sense, this sort of scripting is much more defendable than simply requiring the crew to mention the required information in their own way.

757toga has listed that guidelines are spelled out in AC 121-24C for US carriers. I would like to also include the locations of the regulations spelling out the requirements for passenger briefings. Other than the required information content contained in the regulations (FAR), and the guidelines in the Advisory Circular and other FAA publications, there is no further guidance on how the briefing is to be delivered. The regulations are in the following Title 14 CFR parts:


91.519
121.571
135.117


Each has a version of the verbiage included below. 

In addition to this, the FAA requires all aircraft PICs brief (or ensure briefings are done with all passengers) the operation of safety/seat belts per Part 91.107. The FAA Safety Team recommends following the S.A.F.E.T.Y. format when Part 91 General Aviation aircraft PICs brief their passengers. The acronym stands for the following:


Seatbelts
Airvents &amp; windows
Fire Extinguishers 
Exits, Emergencies, &amp; Equipment
Traffic &amp; Talking
Your Questions


This example guidance can be printed out at FAAST SAFETY Briefing

The example verbiage of the actual regulations is below:


  §91.519 Passenger briefing.
  (a) Before each takeoff the pilot in command of an airplane carrying passengers shall ensure that all passengers have been orally briefed on—
  
  (1) Smoking. Each passenger shall be briefed on when, where, and under what conditions smoking is prohibited. This briefing shall include a statement, as appropriate, that the Federal Aviation Regulations require passenger compliance with lighted passenger information signs and no smoking placards, prohibit smoking in the lavatories, and require compliance with crewmember instructions with regard to these items;
  
  (2) Use of safety belts and shoulder harnesses. Each passenger shall be briefed on when, where, and under what conditions it is necessary to have his or her safety belt and, if installed, his or her shoulder harness fastened about him or her. The briefing shall include a statement, as appropriate, that Federal Aviation Regulations require passenger compliance with the lighted passenger sign and/or crewmember instructions with regard to these items;
  
  (3) Location and means for opening the passenger entry door and emergency exits;
  
  (4) Location of survival equipment;
  
  (5) Ditching procedures and the use of flotation equipment required under §91.509 for a flight over water; and
  
  (6) The normal and emergency use of oxygen equipment installed on the airplane.
  
  (b) The oral briefing required by paragraph (a) of this section shall be given by the pilot in command or a member of the crew, but need not be given when the pilot in command determines that the passengers are familiar with the contents of the briefing. It may be supplemented by printed cards for the use of each passenger containing—
  
  (1) A diagram of, and methods of operating, the emergency exits; and
  
  (2) Other instructions necessary for use of emergency equipment.
  
  (c) Each card used under paragraph (b) must be carried in convenient locations on the airplane for the use of each passenger and must contain information that is pertinent only to the type and model airplane on which it is used.
  
  (d) For operations under subpart K of this part, the passenger briefing requirements of §91.1035 apply, instead of the requirements of paragraphs (a) through (c) of this section.
  
  [Docket No. 18334, 54 FR 34314, Aug. 18, 1989; as amended by Amdt. 91–231, 57 FR 42672, Sept. 15, 1992; Amdt. 91–280, 68 FR 54561, Sept. 17, 2003]