Inconsistent requirements for suffixes

The spec says

The name of a MetricFamily MUST NOT result in a potential clash for sample metric names as per the ABNF with another MetricFamily in the Text Format within a MetricSet. An example would be a gauge called "foo_created" as a counter called "foo" could create a "foo_created" in the text format.

I read this as a counter name MUST NOT end in _created, because this results in a potential clash.

However, the spec also says

Exposers SHOULD avoid names that could be confused with the suffixes that text format sample metric names use.

Suffixes for the respective types are:

• Counter: '_total', '_created'
• Summary: '_count', '_sum', '_created', '' (empty)
• Histogram: '_count', '_sum', '_bucket', '_created'
• GaugeHistogram: '_gcount', '_gsum', '_bucket'
• Info: '_info'
• Gauge: '' (empty)
• StateSet: '' (empty)
• Unknown: '' (empty)

Here it says SHOULD NOT.

It would be good to have more clarity whether a suffix like _created is allowed in a metric name or not.

Start by comparing the two cited requirements in the OpenMetrics specification, including the ABNF and the listed text-format suffixes. Determine whether _created and the other suffixes are prohibited or merely discouraged, then update the relevant specification wording so the permitted naming rule is unambiguous.