Thank you! I'm aware of what's written in the Tafsir books and the lexicons, you have also the known Hadith of (كيف نصلي عليك؟) that may give more clarity, but what I'm talking about is connecting the meaning of صَلَّى to الرحمة in the context above, it's obvious that it's merely an attempt of intrepreting the verb in a way that makes sense in its context and eliminates uncertainty
*, but it's still not an undisputed and a settled on meaning like you see for another verb as استغفر for example, and because of the existence of other interpretations like المغفرة أو الثناء أو البركة.
The website you quoted from said والصحيح خلاف ذلك (أي كون الصلاة رحمة) which is the view of ابن القيم and was followed by ابن العثيمين, the latter said in his Tafsir:
"وما معنى ﴿يُصَلُّونَ﴾؟ اشتهر عند كثير من أهل العلم أن الصلاة من الله الرحمة، ومن الملائكة الاستغفار، وعلى هذا فيفسر ﴿يُصَلُّونَ﴾ باعتباره إلى الله بمعنى الرحمة، وإلى الملائكة الاستغفار، لكن هذا التفسير خطأ"
And added in another book of his as a support for his view:
"اختلف العلماء في معنى الصلاة على النبي ﷺ، فقال بعضهم: إن الصلاة من الله: الرحمة، ومن الملائكة: الاستغفار، ومن الآدميين: الدعاء، ولكن هذا لا دليل عليه، بل إن الدليل على خلافه، لأن الله قال في القرآن: ﴿أولئك عليهم صلوات من ربهم ورحمة﴾"
*That is due to connecting the known meaning of the verb صَلَّى which is دعا to Allah.