Hi Lal,
You mentioned: Thus it is clear that an ekabījī is a Sōtapanna.
The last two must be the two types of Sōtapanna Anugāmis discussed in the post “Sōtapanna Anugāmi – No More Births in the Apāyās“: “dhammānusārī or a saddhānusārī.
In the Puggala Pannatti ekabījī, kolaṅkolo and sattak¬khat¬tu¬paramo has been explained. Here all three have been explained as “thinnang sanyojananang parikkaya sotapnno hoti…” meaning that all three are sotapanna not sotapanna anugami. The differences between the three are the amounts of time they take to attain nibbana as you have mentioned.
For both dhammānusārī and saddhānusārī, the explanations are “yassa puggalassa sotapattiphalasacchikiriyaya patipannassa…”, which means that both of them are sotapanna anugami.
You mentioned: I am not sure yet how kolaṅkolo and sattak¬khat¬tu¬paramo categories are to be identified with dhammānusārī and saddhānusārī categories.
They are not the same or overlapping. The distinction between dhammānusārī and
saddhānusārī are that the pragna indriya is more developed for the dhammanusari while the saddha indriya is more developed for the saddhanusari. When a dhammanusari attains sotapanna phala he is a dhittappaththo, and a sddhanusari when attained the phala is a saddhavimuththo.