The statement is, simply, wrong. It is easy to find counterexamples, the simplest being the quantum particle in a harmonic potential, that has infinitely many states, labeled by a non-negative integer (in one spatial dimension).

A quantum spin 1/2 particle, also, has infinitely many states, corresponding to, at least, the points of the unit 2-sphere. Similarly for a massless particle of spin 1, incidentally, since it, too, has only two polarization states. What is important is that the area of the unit 2-sphere is finite.

There's nothing special about the number 900. A black hole, when probed by quantum matter does have finitely many states, about exp(A/4), in units where G=1,hbar=1 and c=1, where A =4πR^2, and R=the radius of the horizon, in the same units, but there's no particular limit on the size of the horizon.

Incidentally, the opening statement about the known particles being states of the photon, is, by itself, wrong, independently of the main statement-and is logically independent of it-since the photon is a massless particle of spin 1 and the leptons and quarks are massive particles, of spin 1/2. (It is known that the particles are labeled by representations of the Poincaré group, i.e. by their mass and spin and by the representation of the internal symmetry group).

How to add spins is known and it is, just, impossible to describe an object of spin 1/2 as a bound state of particles of spin 1. (Two spin 1/2 can give an object of spin 1-along, however, with an object of spin 0.)

The internal symmetries are, also, completely different and are, also, known, so it isn't useful to pretend otherwise. It would be more fruitful to first learn what is known about the Standard Model, e.g. https://arxiv.org/abs/2306.08097

Stam Nicolis ,

Thank you for your valuable output. I am paying attention on them.