There aren't that many full time jobs even if you take into account lower tier full-time orchestras. The ~10/year number is based on my experience on the audition circuit. Also, I am not aware of any orchestras that involve one member of the section having a full-time gig and the rest of the section not. You can't have an orchestra with only principal players. You have to hire everyone to have a concert.

Regarding your comparison to number of jobs to a large tech company:

Full time orchestras in the US: ~40

Full Members per orchestra: ~100 (Maximum)

Total Orchestral Jobs: ~4000 (This is a deliberately high estimate)

Google employees: 53,600

Microsoft employees: 99,000

Apple employees: 92,000

Amazon employees: 110,000

You are correct that you can be a part of the "Freeway Philharmonic". You will make between $50 and $150 per service (2 to 3 hour rehearsal or concert) playing maybe 6 services per week. Sometimes you will get paid for mileage. Sometimes the orchestra will arrange for you to sleep at a donor's house. Occasionally you will get a per diem (basically daily pocket money for food and gas). Regional orchestras have between 4 and 12 concert weeks of work per year. There is very little work during the summer. You can pack a suitcase and drive from town to town every week and survive. Nobody has work every week. If you don't work, you don't get paid. I did this for about 3 years. Some people do this for their entire career.

Also, just so you have an idea of the competitiveness level of these lower tier part-time orchestras. A few years ago, the Oakland Symphony had a section flute audition. Over 150 people showed up from all around the world. The Oakland Symphony has 4 weeks of work per year - which would amount to a maximum of about $4000 yearly for that position.

Luckily for me, I have found that I enjoy programming a lot more than performing with an orchestra. Now my life is a lot easier.