Numa, Joraga Chieftain + Sage of Hours + Xenograft

How it works

At the beginning of your combat phase, Numa triggers, causing you to pay to put five +1/+1 counters on Sage of Hours.
Activate Sage of Hours by removing all +1/+1 counters from it, causing you to take an extra turn after this one.
Repeat each turn.

In which brackets is this combo allowed, per Spellbook's Ruthless tier?

1–2 · Exhibition & Core

Spellbook classifies this as Ruthless — not for these brackets.

3 · Upgraded

Spellbook classifies this as Ruthless — not for these brackets.

4–5 · Optimized & cEDH

All combos are allowed.