No, phone will not be treated as single sim.
If you have dual sim firmware inside, even is second imei will be damaged, will be null or 0.
But will be displayed.
If you have single sim firmware inside, will not be shown second sim.
so you can simple dial *#06# is it display 2 imeis, is dual sim firmware.
First or second can be displayed as null or 0 but will be displayed.
If show only 1 imei, is one sim firmware.
In mtk phones exist space for 10 imei's
No matter if phone is single sim or dual sim e.t.c
In dual sim is used 2 imeis, in single sim is used 1 imei, but phone still hold 10 imeis inside.