Short answers first:
- Sudaruska only stuns on charge.
- Use Triglav for lockdown.

IMO, Suda's stun effect is probably because they wanted to guide the swords towards certain playstyles:

- Triglav has STRONG freeze effect with a low chance. It's lower chance, but you have more attempts to freeze because the second swing has the ability to freeze. --> Benefits from having high ASI
Arguably, freeze is a soloist's status because it lets you focus on other monsters or move more freely as long as the freeze is on, so by using a 2-swing playstyle, you can freeze monsters in place, recover, and focus your attacks elsewhere.

- Sudaruska has MODERATE stun with a moderate chance. It's higher chance but only happens on charge, so it pushes the Sudaruska player to a charge-based playstyle. --> Benefits from having high CTR
Arguably, stun is a defensive group status - it makes monsters less dangerous when other people are attacking the same target, and with the charge's knockback, it gets you more room to charge again.

Of course, a Troika line sword welcomes both ASI/CTR stats, but the way their statuses work push them towards certain stats.

Now, in lockdown, you WANT status effects, but unfortunately, charge is discouraged because of two things:
- The status on charge only occurs on the second hit
- Due to invincibility frames, the first hit will trigger invincibility and the second hit will do no damage on a direct hit. In order to chance a charge status (or get its juicy damage), you have to either miss with the first hit, or land the charge on someone in an uninterruptible animation: last slashes, reloads, and charging states (among others) are all vulnerable. If you can land a troika charge on a bomber in mid-charge, it's probably going to kill the poor thing. Everywhere else, it will deal unimpressive damage.

Of course, any experienced heavy sword user will stick to slash1 when possible, but when you run out of shield/boost, it's better to gamble Triglav's second hit freeze than a Sudaruska charge.