plaintext DNS inspection to enforce policies. Assuming that devices fallback to plaintext DNS if DoH/DoT are unavailable, the network administrators could block port 853 with little risk because it is only used by DoT. On the other hand, if they simply block port 443, then all HTTPS websites will become unavailable.
Similarly, if they see an influx of DoT traffic, it could indicate an anomaly. If some similar traffic spikes occur with DoH, then it might not be possible to directly distinguish HTTPS from DoH traffic.