Many people are effectively sheep and will install a company app on their personal phone because "wow it's so convenient everything is all on one device".
That said ... employment is at-will, so there are no real rules here. It's not that different from if you sign up to be an Uber driver you're expected to have a car and a phone that you are willing to use for work, or you can't take the job. Nobody says it has to be the same device as the one you use for your personal email, it's just that you are expected to have a device for the job. So nothing legally prevents them from requiring you to have a device with the company apps on it, in return for you accepting some hopefully big enough salary.
For software engineering, if the salary is on the low end of market I expect work to buy me a work phone, if they require me to install any apps. If salary is on the high end, then I wouldn't fuss about it too much, I could just buy myself a separate personal phone for work with the pile of extra cash, but them buying me one would still be a nice, appreciated gesture.
There is no right, just a personal choice. If you have to lug around the company provided laptop if you want to check your work calendar/email/slack/whatever, you may start to consider using your personal device.
Keep personal stuff on personal devices, and never use personal devices for work either.