Thanks @MikeP64 .
My brother is a goody 2 shoes. He has always complied with BI visa requirements and is never late.
I read through the 2 links (I skipped the immigration act of 1940). The purpose of an onward ticket is to make sure a person does not become a burden on the state.
My brothers ticket was not an

so not a reason to deny entry. An obviously speculative ticket is not defined. Even though not defined that sounds like a prosecutable offence (?). If the ticket had been on ShowPony Express that might have been questionable.
I sent a link to my brother with you thoughts and he feels better. He will visit BI in Dumaguete in a couple of weeks and see what they have to say.

When I have more details after my brothers visit I will add to this thread.
Half the foreigners I know have been here as tourist for years, some decades.

 

My brother stopped at the BI today and told them about his recent entry back to the Phils.
The Immigration officer in Manila told my brother he is not a tourist because he spends most of his time here. She mentioned that he never took his onward flights from the previous 3 times he came here.
The lady at Dumaguete BI did not say the officer in Manila was being harsh or out of line.
He was told to go ahead and get an SRRV.

My brother would like to wait 2 years until he is receiving a pension. With a pension the deposit is $15,000 USD, without a pension it's $30,000 USD. Ouch!

 

Just thinking on this a bit further. One should be prepared to use the onward ticket if they can not get their extension before the ticket date. Definitely try to get the ticket for the full 30 days vs less just because it was even cheaper. A one day overlap this time would be a violation that may or may not get flagged on the next flight in or even the next extension. Something that would never have been noticed by a human a few years ago could be flagged by AI quite easily today.

It wouldn't surprise me if they have a secondary inspection quota and your brother simply drew the short straw last time. The inspector knew your brother was legal or he wouldn't have let him in. My speculation is he intentionally created a point of tension just to test his desirability. Don't need another foreigner that pops his cork if you will. Be prepared not only to use your onward ticket but also be able to purchase another ticket out of wherever the flight lands.

 

I've only entered under Balikbayan. Even then I always had an onward refundable ticket as Airlines in the US don't understand Balikbayan and wouldn't let me board without it.
If that BI officer can see your brothers missed departures he can also see your brother has properly executed and received approved extensions by his own bureau multiple times over his two years.

Philippine Law Firm RESPICIO AND CO had this to say:
Throw-away or refundable tickets: legally admissible, but BI warns that presenting obviously speculative bookings may trigger a public-charge inquiry under Ops. Order SBM-2014-011.
https://www.respicio.ph/commentaries/philippine-immigration-onward-ticket-requirement


SBM-2014-011 does not define "obviously speculative bookings" It is the GENERAL GUIDELINES ON THE EXCLUSIONS OF ALIENS BASED ON C.A. NO. 613, SECTION 29 (a)(5)
ON “PUBLIC CHARGE” The primary inspections should be no longer than 45 seconds. A secondary inspection is limited to 20 minutes. So I guess your brother got 50% off on his lecture, sorry had to put that in there. https://www.immigration.gov.ph/wp-content/uploads/2023/12/SBM-2014-011.pdf

It's late and though I find this an interesting subject I'm too tired to read all of https://immigration.gov.ph/wp-content/uploads/2023/11/1_CA613.pdf
Since this act was written in 1940 I suspect there are newer acts that supplement or supersede parts of it. Good luck!