I am not qualified to adequately comment on the teachings of the patriarchs and venerated sanghans. However, since you asked, I’ll try to present my limited views and shallow understanding.
Concerning the three reasons why Chan patriarchs decided to propagate Pure Land instead of Chan, I do not necessarily agree with all the reasons listed. First because some was lost in the translation from Chinese into Vietnamese. Another reason is the teachings were for another time and culture and therefore the language used is not that clear to the modern day cultivators. I’ll try to present my view in a more direct and concise manner:
1. Dharma Door: I agree that Pure Land is more suitable to a wider range of potentials than Chan which is most appropriate for those with superior roots only. I also agree with the rest as well. It is the reasons that are often provided too. Personally, I’d like to add that the real reason that the above-mentioned patriarchs teach Pure Land instead of Chan is out of their great compassion. Clearly, teaching Pure Land means that they have to teach more pupils. It is a lot more trouble than those of us who do not have to teach can ever imagine.
2. Times: I differ from your quote here. In this Dharma Ending Age, living beings no longer are able to cultivate in a sustained fashion. Chan requires long periods of vigorous cultivation and few are able to do it any more. For example, our Chan Qi typically goes from 3 am until midnight for seven days. Few people are able to keep up with it. The majority is simply scared and would not dare go anywhere near it. In contrast, reciting the Buddha’s name is not as demanding and therefore more suitable to the masses.
3. Potential and conditions: Granted that we are not as blessed in this day and age. I am not so sure about the claim that Chan practitioners secretly practice Pure Land. I’ll submit to you that it is very unlikely to obtain liberation this lifetime for the majority of us. Therefore the patriarchs urge us to seek rebirth as soon as possible so as to get out of the sea of birth and death. Another very important reason why they advocate rebirth to the Pure Land is because we can then attain irreversibility. As long as as we still revolve in the wheel, we often regress in our cultivation.
I wholeheartedly agree with the patriarchs. In fact, those who are truly blessed will understand the importance of maximizing their chances of obtaining rebirth this very lifetime.