I don't see how being on the voting register shows that you are settled. Pretty sure Im on the voting register but haven't been settled in UK for 40 years. If your passport shows endless tourist visas, or a residence visa for Philippines, i think you'd have a tough time showing that you're settled in UK, until you actually take up full time residence there.
Quite right - voting register doesn't prove residency, or more precisely that you are "ordinarily resident", which is the **eligibility criteria for NHS treatment**.
So, what they are trying to avoid, for example, is someone who has lived in Philippines (and so not been ordinarily resident in UK) whizzing back home for some free treatment and then whizzing back to Philippines again.
Basically if you are are a British Citizen living in the UK for more than just a holiday, and can prove that (job, house, rent, utility bills etc) you are entitled to free NHS. If you are not a British Citizen there are a few more hoops as there's proving you are actually entitled to be here in the first place - which you might be asked about...
There is an in-depth document here:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/730141/Ways_in_which_people_can_be_lawfully_resident_in_the.pdfBut it is simpler for British Citizens as they have "right of abode", so if you can prove you are settled on a longer term basis that's all you need. So how to prove you are settled on a longer term basis? There seems to be no hard and fast rules as living arrangements can be quite varied. For example, if you've rented a place for 12 months and have a job that's probably enough. If you are retired, but have taken on a rented place, or are living at home and have utility bills and bills that show you are actually living in UK, etc, that's also enough. If, however you are in temporary accommodation (AirBnB, or staying with a relative) that would probably be a little bit suspect, as you might not be "ordinarily resident". Likewise, bank account would not be enough, as you could have one in UK but be usually resident in Philippines.
I guess it's down to the individual to prove their intentions...