Thank you so much for your explanation.

A Russian grammar book published in Russia shows quite a few examples in which the imperfective infinitive is used
to express a one-time action. One of them is the following:
- Стол накрыт?
- Да, всё готово. Можно приглашать гостей.
I assume that in this case it is absolutely natural to « invite » so the imperfective плиглашать can be used.

I believe that in the previous dialog example I mentioned, « propose » is not thought to be a very natural action and
to be an action as new information, so предлагать is inappropriate.

I am looking forward to receiving comments.