Given: 30 Days Before Passover That We're Obligated in B'diqah

This is a proverbial Chicken vs. Egg question:

Given: 30 Days Before Passover That We're Obligated in B'diqah for various situations - EG leaving one's home -

Which came first?

A. The Obligation to do b'diqah within 30 days is due to "shoalin v'dorshin b'hilchot Pesach 30 Yom qodem hachag"?

Or Conversely

B The Obligation to do "shoalin v'dorshin b'hilchot Pesach 30 Yom qodem hachag" is due to to the Chov of B'diqah?

The Popular Answer is probably A See EG Kitzur SA 112:13 reflecting the Tur O"Ch 429

But this answer seems hard to understand - how does shoalin v'dorshin trigger a hiyyuv b'diqah?

There IS the B alternative found in the Posqim - Viz. That since there is a hiyyuv B'diqah the obligation is to start teaching these Halachot at this time because it is now "mei'inyana d'yoma"

This is the bei'ur of the Taz O"ch 429:1 at the end starting "yeish tzorech ... Ki im b'mi sheyotzei mibeito"

This approach might address the concerns of the Hoq Yaakov there [1] based upon the Yerushalmi.

Shalom
RRW