I believe you might be referring to this changelog entry:
What's new in 7.20.2 (2025-Oct-21 10:28):
firewall - reduce maximum connection tracking entry count;
According to strods, this means the connection tracking size was reverted to its pre-7.20 value:
So I'm not sure what point you're trying to make - it seems rather clear that the connection tracking size isn't the issue here. The PPPoE problems still are reported in 7.20.4.
In general, I find it rather odd that reducing the connection tracking count is presented as the solution to an issue that first appeared in 7.20.
Looking back through the changelogs, the connection tracking count was actually increased in 7.18 - and apparently, that didn't cause any problems up to 7.19.6.
The reduction in 7.20.2 sounds more like a quick hotfix than an actual root-cause solution.
What's new in 7.18 (2025-Feb-24 10:47):
firewall - increased maximum connection tracking entry count based on device total RAM size;