After looking at this more, the problem seems more to be that "penetration" is not a binary operation for HE rounds. It seems to work more like a percentage, so if you do any damage at all it counts on the result screen as a penetration, regardless if it actually went into the tank or not.
I own 207 tanks. My records at Blitz Stars!
Pz.Kpfw. 38H 735 (f) • Light Mk. VIC • T2 Light Tank • Tetrarch • T7 Combat Car • Type 98 Ke-Ni Otsu • BT-SV • T-15 • Pz.Kpfw. II Ausf. J • LTP • M3 Light • Pz.Kpfw. S35 739 (f) • T-127 • BT-7 artillery • M22 Locust • A-32 • Sentinel AC I • Valentine II • Pz.Kpfw. B2 740 (f) • Churchill III • Angry Connor • Ram II • Panzer IV Anko Special • Pz.Kpfw. V/IV • T14 • Type 3 Chi-Nu Kai Shinobi • Cromwell B • Dicker Max • Pz.Kpfw. IV Schmalturm • Stridsvagn 74A2 • Kuro Mori Mine • AC IV Sentinel • T-34-85 Victory • T23E3 • E 25 • Type 62 • SU-122-44 • IS-2 • T-34-85 Rudy • Tankenstein • T6 Dracula • FCM 50 t • T26E4 SuperPershing • KV-5 • IS-3 Defender • T-54 first prototype • Löwe • Type 59