In Jain Dharma the rule is about maryada (temple/puja discipline) and shuddhi (purity), not about “how much skin is seen.”

• Dhoti during puja: An unstitched or minimally stitched white dhoti, kept only for puja, is considered shuddha. For many rituals (like abhishek), men remain bare‑chested or use an uparna/uttariya. This shows simplicity, humility before the Jina, and freedom from attachment. This practice is accepted in both Śvetāmbara and Digambara traditions for laymen during puja.

• Shorts: Shorts are stitched, casual, often above the knee, with pockets, zips, elastic, etc. They are everyday outerwear, not dedicated puja‑vastra, and are treated as a‑shuddha for temple rites. They also breach modesty maryada set by temple committees. So even if they cover a similar area, they don’t meet the purity and decorum expected for worship.

• Śvetāmbara: Laymen typically wear a clean white dhoti (and optionally an uparna); laywomen wear sari/salwar suited for puja.
• Digambara: Laymen also use a dhoti/angavastra for puja; ascetics have their own distinct rules.

Always follow the local temple’s posted maryada; most explicitly disallow shorts and prescribe simple, clean, preferably white puja garments.