A non-provisional teaching?

[Inge]

"Ananda, consider this example: when a person who has pure clear eyes looks at clear, bright emptiness, he sees nothing but clear emptiness, and he is quite certain that nothing exists within it. If, for no apparent reason, the person does not move his eyes, the staring will cause fatigue, and then of his own accord, he will see strange flowers in space and other unreal appearances that are wild and disordered. You should know that it is the same with the skandha of form."

(From The Sutra of the Foremost Shurangama at the Great Buddha’s Summit Concerning the Tathagata’s Secret Cause of Cultivation, His Certification to the Complete Meaning and all Bodhisattvas’ Myriad Practices.)

Is this a ultimate teaching of the Buddha?

[LastLegend]

"Ananda, consider this example: when a person who has pure clear eyes looks at clear, bright emptiness, he sees nothing but clear emptiness, and he is quite certain that nothing exists within it. If, for no apparent reason, the person does not move his eyes, the staring will cause fatigue, and then of his own accord, he will see strange flowers in space and other unreal appearances that are wild and disordered. You should know that it is the same with the skandha of form."

(From The Sutra of the Foremost Shurangama at the Great Buddha’s Summit Concerning the Tathagata’s Secret Cause of Cultivation, His Certification to the Complete Meaning and all Bodhisattvas’ Myriad Practices.)

Is this a ultimate teaching of the Buddha?

That seems to describe a stage of meditation. And more like a guidance to recognize skandha mara of form.

[Jikan]

Is this a ultimate teaching of the Buddha?

It really depends on who you ask.