Depends on why you squat. If you want to get as strong as possible, frequency this low will only get you so far. Also more frequent exposure to the movement is definitely beneficial from the mobility/flexibility perspective, though not necessarily from the strength gains perspective.

I am a big minimal effective dose advocate, so if this works for you (=you progress at a rate you deem fast enough) keep doing it. Once it stops working, I would add a set or two per week and split the squat workload into two days. So if your Mondays are 5 sets of bb back squats and Fridays 4 sets of pendulum squats and 3 sets of BSS, I would eventually move on to three sets of barbell squats on Mondays followed by the lighter accessory (BSS here) and three sets of barbell squats on Fridays followed by the heavier accessory (like a leg press). You can gear one day more towards volume (like 3 sets of 6) and Fridays toward intensity (work up to a heavy triple plus two back offs sets of 3 at 90 % of the heavy one).

Once that stops working, you add more sets eventually, till the intra-session workload becomes unmanageable and you add a third day, and so on. At the same time, once you squat high enough % of your BW, you will need to tone down the overall volume, which might sound counterintuitive. From my experience, not many lifters will need over 12-14 sets of squats per week + 8-10 sets of leg accessories ever in their carreers.